Of course she knows what she's doing is wrong. I'm not sure what her point is in doing this. However, I do know the more you show her that this bothers you, the more she'll try to rub your face in it. People are perverse that way. I don't know why. It's like bullying - once the bully gets under your skin and you show it, they're going to keep repeating the behavior.
Her - hey what's up?
You - nothing much. How are you?
Her - well, I'm going to go to the mall with my NEW BEST FRIEND.
You - that's awesome! Have fun! (look at your phone as if you're looking at the time) . Oh my gosh, I have to run. I promised my mom I'd do something for her. Have a great time!!!
Be happy and cheerful and then leave. Go find something else to do.
Remember this - when you were little and your mom did something you didn't like, did you flop on the floor and have a tantrum? The answer is - probably. What did your mom do? My mom just walked away.
Kids normally stop throwing tantrums when they realize they don't have an audience. Once your "friend" realizes she doesn't have an audience, she'll go somewhere else.
