I am assuming from what you wrote that you really did tell her directly that the way she was acting was coming across as mean, etc? And then she refused to hear it.

You did fine, except why are you angry? Don't allow her problems to become yours... unless she is your problem..really that it's up to YOU to correct the situation. Otherwise, distance yourself more from this. She must have some reason to have asked you in the first place, as she obviously wouldn't have thought of her being a problem on her own?

If you wish to continue dialogue, ask her why she did ask, and why you, and what did she want for a response... ??? Good wishes with this!