Regardless of whether or not she's using you, you still call her a friend, and so should be one to her. Just make sure you are not going to allow her to take advantage of you. Tell her that she can always ask you for help, and that you will do your best to help her when you can. Make sure that you're not the only source of support for her, or else she will demand a lot from you. Try to get her to reach out to others for support, like her family and other friends. Or those support groups.
She mite be thinking out loud....pertend not to hear her, and see what she ask of you...then start talking about something you want her to hear....
I have many friends that don't like each other, but like being around me........
That is a tough one....she could be reaching out to you or like you had said she just may be using you. Hard call without meeting her in person.
I would need even more detail it sounds like you may want to iron things out with her though
I would give her the benefit of the doubt untill it really gets bad or if you find out she has been lying or if it just seems suspicious to the point that she asks for things that really put you out.
Then stay with her. Even if your friendship is not strong it could become strong after showing that you can be there for her in such a hard time. She is most likely just looking for someone to just listen to her and be there to hear her out when she wants to vent. Or she may even want to listen to your problems to help her forget her own. It will make you feel better if you stick by her since she is so young and going through such a horrible ordeal