If he’s really as fragile and unpredictable as it sounds like he might be, there’s no way I would let him sleep in a bed. I’d be afraid he’d get rolled on and hurt, or that something would set him off and he’d bite the girl while she’s asleep and unable to shield her eyes and face. He’s little and he can’t do too much damage, but this is serious, and I wouldn’t let this dog go about unsupervised until he was in a better place.