Another possibility is that she's broken the dew claw bone--a not too uncommon problem with dew claws. Once your vet has looked at it, he'll be able to make a recommendation for or against removal. Our first setter had his dew claws removed sometime in his first year (can't remember exactly how old he was
) and the recovery was pretty easy.
Could a broken dew claw have caused a limp? You betchya! Owie!!!
I hope your girl is feeling better soon!