If Graendal saw Elza in TAR, taught her some weaves to undo the wards and noticed she was compelled, there wasn't much she could do there. The compulsion would be real world, and as such not removable in TAR.

And as for why Brandon doesn't hint at the presence of someone else... that is obvious. He doesn't want to spoil the surprise.

My reason for suspecting Granedal is that this whole scene was very psychological. Several things were necessary:

1) Semirhage would try to torture Rand. I think Granedal's comments on Semirhage's cold, one track mind in the prologue suggests that she would have foreseen this.

2) Rand would not respond to the torture, so Semi would have to turn to Min. This in turn would remind Rand forcefully of Ilyna, and this would drive him to seek the TP.

The 2nd point is what cinches it for me. Graendal has studied people with voices in their head. It is possible that she knew what Rand's being in contact with LTT meant, and thus engineered this to give him pain of heart as commanded.

The plan seems to cerebral and psychological to be Moridin's. Too indirect, playing too much on the emotions of the characters involved. That's the signature of Graendal.

Further, the only thing her prologue showed us was that she knew Semi was captured (and that Moridin was so pissed he was ready to sacrifice her) and that she was ordered to mentally torture Rand.

Both these facts were critical in a crime that depended on the psychology of the victim. Not seeing some involvement from Graendal in this seems absurd to me.