That's really slimy of her considering your offer. People are greedy, and since you said it was a fire that bred her, you can bet she is hoping for a fire out of the egg. I wouldn't have told her what was bred to it before I sold. She likely would have never known what a fire bp looks like, and could have easily sold it back to you.

That's all speculation of course, this person may feel entitled to tell you no for good reason, sorry for the bum luck.