My daughter is a bully and a "mean girl" at school. What should I do?

[Nick]

My daughter thinks she's all that and honestly she is completely gorgeous. She has a little group of close friends and they are kinda a clique I guess. She enjoys dressing up in the best clothes, attracting the guys, and always has to get her way. She's very popular at school and she likes getting that kind of attention. I have to say I spoil her because she's my only little princess, and what father wouldn't want to spoil his daughter?? She's 14 and I already got her first brand new car picked out for her. She's my pride and joy. But recently we got a call from another girl's mom and apparently my daughter has been tormenting this girl because the girl is overweight and unpopular and apparently this girl is very hurt by it. She bullies other people too, talks behind their backs, makes up stories about them, and is downright disrespectful because she thinks she's the best and the smartest. I have to say she is the best but I don't want her to bring down other people. I didn't realize that she hurts people like this till just recently and I want to know what her mom and I should do about it?