Should We Break Up Over Prom?

So, my girlfriend of a year and a half wants to break up with me because I don't want to go to prom with her. Now, she is in two grades below me. I am a freshman in college, she is a junior in high school. We went for my junior prom, my senior prom, and now it is her junior prom. She wants me to go because she doesn't think it's fair that she went to mine but I don't want to go to hers with her friends, after we went to mine with my friends. She wants to break up because she doesn't think anyone will ask her to go because she is dating me, and because she doesn't want to go alone, and if we break up, someone might ask her. Now, I don't want to go because I would feel like a huge tool. I have no friends in high school. I know a lot of the kids but I don't want to look like an idiot. I also don't have much money, and I would rather spend it on a really nice date in New York City, at an amazing restaurant, and buy some nice clothes for her. I also said she could back out of something for me and I'd make it up for her. She says that she doesn't want to do that however. She said she would pay for it, but as a man I wouldn't feel right letting her pay $220 ($120 for tickets and $100 for the tux). Now, I feel bad because I love her and want to make her happy because this is important to her, but the only way she will be happy is if I go to prom with her, but I really don't want to spend the money or look like an idiot. Should we break up so she has the opportunity to have someone else ask her, then get back together, or stay together and me not go, or should I look dumb and go?