Yes, this is a deformity. A "birth defect" if you will.
And the breeder had to have known about it. I've heard that some people think its due to temperature problems during incubation, other people think its a genetic defect.
Either way, this Ball Python should have NEVER been sold that way. If anything, it should have been GIVEN away with full disclosure. I don't believe for one half of a second that the breeder did not know about it. To sell this snake, and to someone new to the hobby as well, is highly un-ethical.
Call her out on it. IF she still ignores you, I would expose her and her selling practices. There are several places that have a "Board of Inquiry" (including one on this forum) where you can review a seller and their practices, and this is certainly a case where I would do this, because this is truly un-acceptable.
Of course its not the poor snakes fault and it deserves a good life, but you don't sell one like this to an unsuspecting buyer.
About the eating..well, I have heard that some Ball Pythons with an overbite eat normal. So I'm not sure if this could be a factor. Does she ever flick her tongue ? I would double check the husbandry. Are all the temps and the humidity "spot on" ? Does the snake have enough hides and privacy ?
I'm sorry you were introduced into this hobby this way.