We found my cat after she was missing for a week... what should we do?

was it neutered?.. if not its probably found herself a "friend" maybe that's why she is acting this way... and the lost weight is probably because she just didnt eat and that shouldnt be a big deal as long as she doesnt refuse to eat or anything... your cat will most likely be just fine, dont worry and dont let her escape again =) if you are still worried calling a vet wouldnt hurt =)