Friend troubles

I have a friend at school. Let's call her C. C had been one of my later friends after I moved 6 -almost 7- years ago. C is always talking to me. She is one of those people that are really too young to date, but if always in "relationships" that last about a week. I talk to her when she needs help discussing personal problems and or relationship problems. I provide advice to her whenever possible. BUT: When I try to talk to her about my problems, she brushes it off and pretends that it doesn't matter. I know she is not a very good friend on that way. The problem is is that when we had an argument and we weren't talking for 2-3 weeks, she was bothering me to be her friend again. C loves gossip, just like me. We love to talk about gossip. But then again, she doesn't open up to me in the way i do.

Pros:

talk to C about gossip

Friends for a while

Cons:

can't provide comfort and or help when I need it

Thinks she's more superior that anyone else

Rude to most other people

Help me. I want to know before the beginning of the next school year (September 3,2018) so it won't seem like I'm dumping her.

Should I talk to her?? Slowly drift away?? Keep being her friend?? I don't want to seem like a bitch for leaving her, but I don't know if I would be doing the right thing or not.