It could very well be a phase, so I wouldn't go breaking it off just yet.
Most girls go through that phase in high school, but she hasn't had the chance to until now. In my experience I went through nearly the same thing when I was a teen. I was short, chubby, bad perm, glasses, braces, you name it. No guys paid any attention to me and neither did the girls. I only hung out with my also-not-so-attractive friends, doing dorky stuff like band, roller skating, and liking dogs. Then, I hit a growth spurt and grew 5/6 inches, got the braces off, perm grew out, got contacts. And suddenly I started getting attention -- and I loved it. I thought, well if look good and I'm getting attention now, imagine how it would be if I looked GREAT! And so started the dieting and working out, 3 hour beauty routine, never leaving without everything done. And it worked. I got a lot of attention, girls wanted to be friends, guys wanted to date me, and even better, I had my pick, and didn't have to be stuck with no options. I ditched my old boring friends and started a pretty much new life. Unfortunately for me, I liked it a bit too much and wound up going off into eating disorders, drugs and so forth. But even if I didn't, I still grew out of it. 3 hours isn't realistic in a real life setting. Neither is maintaining a very low weight with high exercise and immaculate diet. Guess you could say I grew up.
She might eventually get over the 'high maintenance' thing when the rush and the newness wears off. Or she might not. Or she could get worse and ditch you. I would try talking to her about your feelings, you won't know until you talk to her.