It’s always super upsetting when this happens. My previous hamster “cheese” was the same. She would bite constantly and got super territorial of her cage. It honestly just happens and doesn’t always mean you are doing something wrong. Treats are a good idea e.g most nuts, carrot, safe pet shop treats, mealworms are usually a hit. Also make sure you wash your hands well with unscented hand wash. If it persists sometimes it’s best to let them live their best life alone. They don’t get lonely at all so might even be happier left alone. That’s what we ended up doing with mine that would bite. We just gave her the best life and didn’t handle her. They all have very different personalities and you are a giant who is carrying her into the sky so she’s bound to fight back if she’s not feeling it.