My ferrets favorite “toy” seems to be my belt, particularly, chewing at the metal belt buckle rather aggressively. I’m only concerned that this might damaged her teeth, but I’ve seen ferret toys that are metal bells. (I’m a new ferret mom)
She looks quite young so she is probably teething. Chewing on your belt buckle will probably be giving her some relief but it won’t be good for her teeth or gums so try not to let her do it and provide her with a safe alternative.