I don't really know what you want to know. If it's only a one time regurg (I hate to say this--I know how touchy some of the topics can get) but I personally wouldn't worry about it. If you were handling her within twenty four hours after that particular feeding--that'll do it. Twice in a row--stool sample it. If you can't get her to eat FT, but she is eating Live...why are you switching her? If you really want to switch you will need to dangle it in front of her for a minute or two for the first couple of times. Also, you can try dipping the FT in chicken broth (my snakes all love this).
I hope this helps some...
~Jim