First of all, not only girls break hearts, and I'm offended that you would think that way. Guys are horrible: they'll lead you on so much and get what they want, and then never call you back. My friends cry incredibly over guys that they thought looked super hot, then ended up going to a party with them. It all seems great, she gets drunk, he gets drunk. One thing leads to another, and hopefully he doesn't convince you (however much that might take) to go all the way. Even if he doesn't, he never calls back. He breaks your heart.
BUT THANK GOD IM A LESBIAN.
Anyway, yes I have had my heart broken by a girl. It was.. about a year ago, now. I really don't like to think about it, and..well this is just making me think about it, haha. But yeah, it's happened to me.