While I am not sure what part you on, and assuming you are on 1.02. After you talked to the purple haired girl you must have a conversation with 3 ppl, while that didn't work the first time or it might just be you need a new person. I tried different ppl, I think I did the Principle, TA and her. While I can't say for sure how I did it I believe you just need to do perfect conversations. You may just need to end on one but you should get a cut scene where she goes, that went well. And if that doesn't work just try 2 ppl conversation.
O forgot to mention I did it during the week at school, while I can't remember if that was important or not I do know that she has a lot of BS quest that are timed to weekday and weekends and make you go through a whole week doing nothing, to then do 1 thing on the weekend to then do 1 thing on the week and then again 1 thing on the weekend again......