My friend won't pay me back?!?

I've been really good friends w/ a girl I met this school year. I thought she was nice and stuff, but now I'm having my doubts. Anyway, last weekend, I invited her to go to the mall w/ me, my sister and my mom. We went to the movie theatre and then we had lunch at Johnny Rockets. She said she was going to pay for her movie ticket (when we were paying for the tickets we hadn't talked about lunch yet) because she had brought her money. In the end, my mom had to pay for her ticket because supposedly just because we payed for the tickets through the little monitor thing she couldn't pay for it (excuses!). Then, after we left the theatre we went to eat. I thought she'd at least pay for her meal but no. She didn't use her money until we left the restaurant. My mom payed for everything and I felt really bad about that because she's not getting paid as good as she used to. Well, she saw this cute bag she wanted. It was $25 plus tax and she only had $20. Being the good person I am, I took out $5 dollars from my purse and gave them to her. Then, because of the taxes we needed a dollar more so I asked my mom because I hadn't brought any more money. FIrst, she refused. She said it was too much money. In the end, she took it. She bought the bag and this whole week she's been practically ignoring but she wears the bag/purse thing to school. I reminded her twice that she had to pay me back and she just said "yeah i know". She keeps hanging out w/ one of our other friends and she wont even say hi to me anymore. Her and our other friend switch book bags every day and the other day she was about start doodling on the bag. I'm not mad that I had to pay for everything when we went out last weekend but I'm just mad how much of a jerk she's become. Especially, because its been more than a week and she hasn't payed me back and she said that she supposedly pays EVERYONE back super quick. But apparently not really. My mom is pissed too. She told me to just act natural and don't mention the money anymore. I don't feel I should stop reminding her. I think I don't have to accept the fact that she doesn't have to pay me back and that she can keep being a jerk whenever she feels like it. Should I go w/ what my mom says or confront her? If she won't pay me back before the school year ends (ends June 9 2011) what do I do?