If the boss is at a certain distance, I usually run at her and do a running attack. The boss will usually try to attack, and you'll usually beat her. Sometimes she'll teleport so be careful if your attack whiffs. If she's hitting you with her punch string, do a back+F reversal. She's frustrating, but beatable. It took me some time, but I was able to unlock all the costumes recently.
I'm down to playing this game online as well against you folks.

