Rush to her house as fast as you can and help pick out a fabulous outfit!
Talk to her on the phone and ask her about a bunch of different clothes she owns
Just tell her to pick an outfit!
Buy it for her and not even care if she pays you back! As long as she's happy, you're happy!
Offer to buy it for her, but when she says no, you give up.
Tell her to either get over or get some cash.
Yell at the mean girl until she goes and apologizes/does something nice for your friend. Then you go into the bathroom, make sure your friend is okay, and stay there the whole night of you have to.
Go to the bathroom and see if your friend is okay. Once she's stopped crying, you go out and enjoy the rest of your prom.
Just know that she'll be fine the next day, so you don't do anything about it. It's not like it was the end of her life!