I'm sure they would if I was referring to a female. (which was my intention.)
You did refer to a female. Online translators just aren't very smart. Your sentence reads, "She is hot, I want to touch her end." The possesive pronoun his/her does not change based on the gender of the person doing the possessing. It changes based on the gender of the thing being possessed -- in this case an end, or bout, which is a masculine word whether it's attached to a girl or a boy.
However, I don't know if the phrase "elle a chaud" means anything more than that she is literally warm, in french and I don't think bout means butt in any sense of the word aside from end. I could be wrong about both, though. I think what you want is:
Elle est chaud. Je veux toucher sa cul. (even then I think "Elle est chaud" might be stronger than just "She is hot" and more like adding a bit of "ready to go" in there too).
edit: ...sorry, I'm a geek. And I'm learning French.