It sounds like she isn't ready to accept him yet. When she is ready, she will answer his head bobs with a deep low slow bow/pushup. He will grab her by the back of the head, possibly drag her around for a little ways and then kick at her tail with his back legs. If she is receptive, she will raise her tail and he will curl his underneath and
voila! If she isn't receptive, then pretty much nothing happens except some biting and then he leaves.
