I've had the same problem as well. My first playthrough I did the prologue and the first morning where you have to wake Sasha up (after going to the instructor's quarters for the first time) clicking Sasha did nothing but reset the music. I reset and played a new game, this time without the prologue, and this time clicking Sasha worked. Then I tried another time with the prologue, and it didn't work again. It may have something to do with the prologue, or it may not cuz I didn't do everything in the exact same order in each playthrough, but there seems to be a bug with something to do with waking Sasha up the first time.not working how? there's a morning when you don't have to wake her up for example (by talking to sis in the same room you learn Sasha'd already left), you just go straight to the fields.
If you've completed her training branch, you can't wake her up right now. There's simply no content there yet.
I also got the Historia event about the stalker outside the window before the morning where I had to wake up Sasha in my second playthrough (without the prologue), but not in the other two. It might have something to do with that trigger as well.