Not really a bug, more of an oversight on Avenger's part. While you have Sasha locked up, it makes sense that you can't invite people over. But after you let her go, there is no reason why you can't have guests. Unfortunately, Avenger only addressed 2 conditions - you NEVER trained Sasha and you're training Sasha, so even after you let her go, as far as the game is concerned, she is still in your apartment.
AFAIK there are two solutions: reset Sasha's training parameter via QSPSaveEditor or, through QGen, delete the lines that check her training parameter for every guest.