Well if the feeder fish was bad then a few things can happen. If she vomits it will be bad. They prolapse their stomachs to do so which can be fatal if the frog cannot get the stomach back in. You would need a Vet in a matter of minutes.

The frog can keep the fish down and it not actually be the problem. Could just be stressed due to the climate changes from winter.

Signs of a bad feeder are similar to toxing out syndrome and the frog will beging to bloat and possibly have diarrhea.

I would still see a Vet before anything that cannot be handled at home happens.