You can ask her by talking to her in the evening at the convenient store.
Discover Midnight in the classroom the 1st time -> Talk to Tsuyu next day at school to find out that she's ignoring you -> go to your room in the evening to unlock Tsuyu's room -> go to Tsuyu's room in the evening. She doesn't want to talk -> go back to your room and watch a short scene -> next day, go find Midnight in the convenient store and talk to her.
You did everything here?