The question here is, “Do you still have feelings for her or not?”
It’s obvious that she’s still interested in you by the way you describe her. It’s just that she became confused as to why you unfriended her and such.
If you have no feelings for her anymore, as in truly, it’s up to you if you still wanna be a casual acquaintance with her. Accept her friend request if you want. (Is it on facebook?) Just act normal. When you see each other, still be friendly. “Hey, what’s up?” Act casually. I know it’s not easy to forget about her ’cause you always see her at school.
The best way to forget about her is to focus yourself in other things. Like school exams, exercising, staying fit, find things that you’ll be interested in, like sports, find some hobbies to do etc.
If you find another girl that you have a crush on, or interested in, the sooner you’ll forget about the previous girl.