Hi. It sounds like it's resource/food aggression. It doesn't matter if she gave him the toy / treat in the first place. The yorkie would see it as his and try to protect his prized possessions and consider her as a "thief". Mine bit me too, especially when he was eating something he shouldn't and I tried to grab it out of his mouth. Drew blood / puncture marks many times but now (thankfully) I've got it handled
Locking him would just exacerbate the issue. He barked/growled at her, probably as a warning, and since she ignored said warning, he bit.
Do read more about handling resource aggression. She can do it herself. There are also plenty of videos on youtube about it, but in the meantime, here's what I do with my puppy: when I feed him, I only put half of his food in the bowl. Then when he eats, I approach slowly (he'd then look at me suspiciously) only to put more food on his bowl. Then I'll pet and praise him and put more food again. I do this until he associates my presence with more food/treat and can eat with me beside him at ease since he now knows I'm not a food thief
Try it very slowly if the dog would just snap at the sight of you. Hand feeding also helps to bond better with the dog
Also, do this with the treat. Don't just leave toy/food/treat lying on the floor - sometimes dog thinks they pop out of nowhere and try to protect it. As for sleeping, try to give him treats (in small bites) whenever she touches him. He'd slowly associate her touches as a positive thing. Do this, increase the frequency until she can handle and pet his body freely.
Oh and google "nothing in life is for free dog training". Basically it's the idea that in order for them to have food/treat/toy, they have to do something first (sit, lie down, etc). Don't give in when he misbehaves, so he knows he gets good stuffs when he's calm and play nice. Do update us and all the best.