Poor girl , she could be constipated.
Keep her warm, a towel to cuddle into.
Mash up some of her pellets food with hot water to make a sloppy paste and get a Calpol syringe (go round NDN with small children if you don't have one. They might have a spare syringe)
Put the syringe just behind the front teeth and squeeze a bit, let her chew the syringe them she'll swallow it, if you squirt it too much it can go down the windpipe.
She sounds a bit dehydrated , the sloppy mix will give her water and fibre, but its time consuming and messy.
Once shes had some, give her hay and let her sit quietly.
She might let you massage her tummy, she might not.
She might like to sit in a bath of shallow warm water if you can keep her warm and get her dry. Depends on how she is, she might not want any handling.
Hopefully you'll get an improvement in output.
Look for anything plastic she might have chewed , might be a blockage?
Keep a check on her pooh.
Good Luck.
This is just an interim 'help' if she doesn't improve drastically then she'll need a vet but a sudden swelling is usually because the pooh ain't coming out.