Yesterday my aggressive, anti-social cat came back. She disappeared at he end of March. We thought she'd chosen to leave once the weather got warmer as she hated the new kitten who arrived in October.
Turns out she was lost 
She looks terrible. She's a big cat who weighed 5.5kg. Not fat, just big. Now she's just 3kg. And she's so quiet and traumatised. Now we're all her best friends, even the young cat. When I pick her up I can feel all her bones, there's nothing to her.
Do I need to take her to the vet? She's eating and drinking ok but is moving like a very old cat ie needs help to get on the bed as she can't jump up. She's only 8. Or should I just keep an eye on her and give her time to recover?