Akita thinks Chihuahua's nips and snarls are an invitation to play. Help!?

Jasmine is a large Akita mix breed while Thor is my sister's smaller Chi mix who just moved in with us. While Jasmine loves having another dog in the house -and someone else to throw a toy every once in a while, she's not very well socialized and when it comes to playtime, she's not so great at evaluating Thor's reactions to her advances. Thor was terrified of her size for a month. Now, they can cuddle together, and they've even played together a few times, but Jasmine has WAY more energy then Thor - he's mostly happy with looooong naps, and his human cuddles.

But when he's up and moving, Jasmine invites him to play by licking his face and poking his side with her nose. Thor ends up snarling at her and showing teeth. Jasmine left him alone after that for a bit, but now she thinks that's just his way of playing back. So she has started opening her mouth and poking him. She has never bit him, but he's now retaliating with a fairly gentle nip- usually on her face or her legs. We scold him, and tell her to leave him alone, but she really thinks this is his way of playing with her! I'm worried he's going to really bite her hard, and she'll bite back and he'll (or she'll) get really hurt. In attempt to avoid a fight, how can i teach Jasmine that this is not his way of inviting play (or is it?) And helping Thor learn that she's not going to hurt him if he just plays along.