I think they are most likely purebred if she knows the weight of both parents. Maybe both parents are on site so you can see for yourself. I wouldn't say there is boston terrier in them and that sounds like the only option in that household. Boston terriers have that smashed-nose look going on which would be a very dominant gene. Go see them and ask questions, ask if there is any possibility she was bred to another dog. And let her know you don't trust paperwork. Either way, they are gorgeous...well worth a little house work.
