Given we never saw a body, and Brandon refused to confirm whether or not she died, it was expected that people would start theorising about her potentially living--but is there any reason to do so beyond simple nostalgia?
The point that may suggest that things might have gone differently than they appeared to lies in the question--why didn't Graendal flee? Rand himself states that, "She will vanish the moment I threaten her, running to one of a dozen other refuges she is sure to have set up." [tGS; 37, A Force of Light]
Through Ramshalan she knows that Rand not only knows precisely where she is, but is thinking about the possibility of killing her at that very moment. Even if she thinks that Rand was playing by her rules--as Rand wished her to--why doesn't she run anyway? By everything that is said about her, she should have--unless she had reason to think she knew exactly what he planned. And that's the oddity here. Nothing in what Rand gave her via Ramshalan should have been strong enough proof that he intended to play with her that she would disreguard the danger of the Dragon knowing her exact location.
She should have run. Why didn't she?
Why Didn't Graendal Run?
The explanation I gave above serves--she would have stayed if she had reason to think she knew Rand's plans, and would be able to counter them safely. So if she didn't have enough to be certain that Rand was only going to play with her, could she instead have been expecting the attack? And if so did she have clues to lead her to the specific nature of the attack Rand intended--the balefire and the compulsion test? Firstly, we have this...
"I have to peer into her eyes, see into her soul, and know that it's her that I face and not some decoy. I have to do that without frightening her into running. How? How can I kill a foe who is more clever than myself, a foe who is impossible to surprise, yet who is also unwilling to confront me?"
[tGS; 37, A Force of Light]
Whether he meant to or not, he actually lays down his desires there. Specifically he wants a way to kill Graendal before she has a chance to run, and yet ensure it leaves evidence that she did in fact die.
Still, that's fairly generic. If Graendal realised there was to be an attack, and only had that, I'd say she still would have run. Too many attack routes, no idea which one Rand might choose, and thus no way to be certain enough that she could foil it and survive. So is there anything that might have directed Graendal to Rand's method?
Why Did Rand Send Ramshalan?
So, acting under the premise of this theory--that Graendal was looking for the attack, and planning how to oppose it--then there is a question that raises itself--why did Rand send Ramshalan? It wasn't to ensure she was there, because she could easily have travelled the second he was out the door. It only served to alert Graendal that Rand knew where she was, and thus that she was in danger--which raises the chance that she would flee, one of the two things Rand stated in front of Ramshalan that he wished to forestall.
So if this violated one of Rand's desires, logically would it not being doing so in order to serve the second. In effect it points out, should Graendal have been looking for the attack, that Ramshalan was to serve as the proof of her death.
The Stepping Stone To Rand's Plans: Compulsion and Balefire
That idea that Ramshalan was sent to become the proof of her death opens up the plan. What would be assured if Rand sent Ramshalan to Graedal--she'd compel him. How would that serve as proof of her death? It gives Rand a recent piece of her work to test should she be balefired--and how unlikely would it be for her to consider that Rand would use balefire on her? Not very--he's used it before; it's highly destructive and cannot be shielded against, which fulfils his requirements that he be able to kill her before she can run.
Of course, predicting balefire as the weapon, and predicting that he'd balefire the entire palace are two different things. However it has been pointed out that Graendal was charged with making psychological warfare on Rand--that would necessitate studying him, which would mean that she would have a very, very good understanding of what how far he was gone, and thus what he was capable of.
Irrespective, she needn't have actually predicted he'd balefire the palace. She could have made a decoy masked in illusion for him to personally balefire. For her to have lived we don't need for her to have guessed everything, just enough, and once Graendal began preparing to meet an attack its next to impossible she didn't consider the possibility of balefire--this is a woman who used human blood on her letters to Inturalde despite doubting any Third Ager could tell the difference between human and animal blood--she fills her plans with redundancies.
Defeating The Compulsion Test
The first method I've seen suggested for how she might achieve this is in having tied off the web so it could unravel on its own. There is the question of why Ramshalan is completely undamaged, but then Nynaeve states that this web is lighter, or more subtle. "Yes. Rand, he's under a heavy Compulsion. There are a lot of weaves here. Not as bad as the chandler's apprentice, or maybe just more subtle."
Graendal knows everything there is to know about Compulsion, and she would know how to place a compulsion that could unravel without harming the individual. It likely wouldn't be as effective in the purpose of compelling Ramshalan, but then the suggested purpose here wasn't compelling Ramshalan, but deceiving Rand.
Of course this raises the question of timing. How did Graendal set the weave to unravel at precisely the moment that Rand balefired the palace? I've seen three answers to this: The first is that she held a inverted web which she released when she saw the palace destroyed, thereby unravelling the web. The second option is that she set the web to unravel after being delved--this is a reasonably logical idea--if Graendal perceived the compulsion would be the test, then she'd perceive it would be tested twice. Before and after. They test it before, the compulsion dissolved, Rand balefires, and then they test it again and what do you know--all gone.
The third option is that she set the weave to unravel in the face of balefire. We know from [KoD; 3, In The Gardens] that Graendal has at least some understanding of what the effects of disturbances in the pattern can be, so it’s not impossible she set the weave up to collapse in the face of the warping that resulted from the use of balefire. Note that Nynaeve says that "There are a lot of weaves here", and that she clearly doesn't understand them all. One could easily be designed to trigger and unravel in the face of the pattern rippling.
The second explanation for the disappearance of the compulsion runs that Graendal either trained another woman and let her weave the compulsion, or else linked with her and used only her power to weave the compulsion (something we know to be possible from both the a'dam, and Narishma in [WH; 54, With the Choedan Kal]). I suspect if either is the case then the latter is more likely given the skill displayed in the compulsion.
After that Graendal chucks a runner, and leaves the hapless woman to her fate (likely disguised by Mirror of Mists as Graendal in case of an attack, with compelled commands to ensure she dies satisfactorily at Rand's hands), thereby successfully convincing Rand he's succeeded in killing her, when in fact he has only killed a decoy. In some ways it could be said he gave her the idea himself.
Of course this raises the problem of where Graendal came by a channeler so swiftly. I've seen two ideas suggested. One, chronologically this occurs after Aran'gar and Delana flee the rebels. Given Aran'gar's new alliance with Graendal (which Graendal helpfully mentions in the prologue), its not inconceivable that she sought out Graendal after fleeing, and that it is Delana who gets supernuked by Rand.
Two, Graendal gathers the powerful and the beautiful. It's not inconceivable then that she has snagged an Aes Sedai, Wise One, Windfinder or Ayyad. The woman herself would be under heavy compulsion, but that doesn't stop you channeling as far as we know, and women gain none of the protections from compulsion that men gain from saidin, so it wouldn't be a risk for Graendal to keep one under the level of compulsion she places on her pets.
In conclusion, that she did not run in the beginning is strange, and does indicate she thought she knew precisely what was going to occur, and thought she could deal with it. In contradiction to that, what Ramshalan told her seems to contain little in the way of proof that Rand merely meant to play with her, as Rand suggests was her deduction. Thus the fact that she did not run is a problem. From there Ramshalan's presence and knowledge could well have guided her to figuring out the specific nature of the assault.
Ultimately the only real evidence to suggest that the stated course of events--that she died--did not occur is in the relative oddities of her providing Rand with precisely what he wanted despite being made aware of that by Ramshalan, and that she did not run immediately upon realising Rand knew where she was. Her surviving does follow a logical progression, but by and large it is far more likely that events fell out precisely as they appeared to, and Graendal is dead.