Well, if it hadn't of been leaked I wouldn't have it on my itunes. (As well as Christina's, because I wanted to make sure she got paid..plus Christina's adorable.)
I don't think a song being leaked will stop a song from bought. There are quite a few different versions of popular songs floating around from their original writer. (Adam's "Whataya Want From Me" was written by Pink..and Britney's "Perfume" was written by Sia..both available by Pink and Sia online.)
Unfortunately, things get leaked and things get spread around with the technology we have. As much as it can be bad for Haley..there's also a possibility that it goes viral, and Haley gets a viral single.
I hope though, in the future people know...if Haley has written a song and it's been published..and someone else is singing it, she's getting paid.