Update - the swelling has gone down almost completely.

She hasn't been fed for almost two weeks (due to be fed this weekend), and she gets medium sized rats, so I don't think it's from feeding.

The substrate in her cage is newspaper, there are a few fake plants... wonder if she would be silly enough to try eating a plastic leaf?

So I guess for now I'll keep a close eye on her to see if any swelling returns or if she shows any signs of discomfort or injury. I'll be especially interested in how she deals with eating her rat tomorrow.