Nope! One of the main arguments they have is her inability to reach orgasm. It drives him nuts. So, imagine another guy hitting that g spot just right. He won't risk it, so there will not be any swapping.
There is a definite pattern to Anna's sexuality. The deeper she goes, the deeper she needs to go to get the same high. I think she recognizes this and it stops her from going too far because she's afraid it will sexually break her and she won't enjoy sex at all anymore. Trust me, if she didn't have this fear, she would be doing hard core bdsm porn. Believe it!