That's just grasping at straws, IMHO. We don't know that Semi would have felt Graendal - it depends on a whole lot of things we have no idea about. Where did SH meet with Elza initially? Was it near enough to Semi that she'd have felt if Graendal channeled? Even if it was near enough, perhaps SH could have prevented Semi from feeling anything - we know he has special abilities with blocking Shadow minions from the True Source. And, even IF Semi felt something, she'd have had no idea what it was. For all she would know, it could simply be Nynaeve channeling. To suggest that she would immediately leap to the conclusion that another FS was nearby, and that she was being set up, is highly implausible.

Not to mention ... if Semi could have felt Graendal remove the Compulsion, then she could have felt her delve Elza, too. There's no reason to think that the delving would be safer than the removing, which is essentially what you are suggesting.