poor baby that's so sad! At least she found her way home though so she can be reunited with her babies. Have you introduced them back to each other yet? Do it very carefully, watch like a hawk, since she's in severe pain she could reject them. She'll do fine on three legs, one of the kittens I found last year had a missing left front leg, not sure what happened probably a raccoon or coyote, but now she's healed perfectly and zips all around her new home. So your momma cat will do just fine. she definitely should be spayed though, hopefully she didn't get pregnant again during her time away from home. Have you thought about talking to a rescue group? Maybe they could find homes for her and the kittens. Putting her back outside might not be the best option, since she does only have three legs she'll be at a slight disadvantage being able to defend herself. You're doing a great job, it was very kind of you to take them in!! Good luck keep us posted