That's really weird. I'm not as knowledgeable as everyone else here, but the flesh near your belly button ring probably smelled different to her. I noticed my hedgies like the smell of sweat or human in general before being washed and will nibble at things that smell like it, so I always wash areas I know they'll be before I hold them.
I've never been chomped on before, I imagine it would hurt quite a bit though.
I wouldn't be worried about infection as long as you've taken her to the vet before and she had a clean bill of health. Just in case though, I'd clean it with some peroxide if it's still swollen and you have that lying around the house. Mix it with a little water if you're worried about it affecting the piercing. I always did that when cleaning a lip piercing I had a long time ago.