Is she on the balcony at night? Or in her laboratory at night?
If not could you send feedback via the feedback form?
Yes, she is neither on the balcony nor in the lab. About feedback, ofc i can, but I can't promise anything because our internet connection might not allow "us" to do this, unfortunately :( I can only say that I've completed the Rainbow Dash quest chain so far. I offered the gold leaf to Twilight Sparkle when I had the chance. I haven't started the other characters' quests yet. Game version 6.3.2, 6.4.0, 6.4.5.
But anyway what should I do in this situation? I restarted the game, got to the same point, and she was still nowhere to be found.
I tried sending feedback numerous times, but unfortunately, my internet connection wouldn't allow it, even with a "three-letter" service. But it turns out I found a bug. It's all about the golden leaf and the dialogue with Twilight Sparkle, after which she disappears. I tried playing through again, but ignoring all the explanations about the items for the mirror. And voila, the script sent me to the room, and the next day she's standing on the first floor, as if nothing had happened.
The problem is with the answer about the leaf: when you click on it, the script breaks. That's all I can say: I tried it in different languages, and the result is the same. Look at this code snippet.