What should I do when a friend is mad @ me and thinks I know why?

-One of my friends is superdeduper mad at me and thinks I know why but truthfully I don't. Ive emailed her and chatted with her online but she never answered in fact she said, " You know why so just log off." and she also said, "Shut up you know why!" I'm not mad at her and I have absolutely no idea why shes mad at me! HELLLPPPP!!!!Tell her as honestly as you can. Ask a friend to as her why shes mad at you , then tell her

or without knowing what she means say your sorry a really sincere apology
If she's not going to tell you, then maybe she just wants attention. She's probably just feeding her anger. I would leave her alone for awhile.
think really hard did anything ever happen?