What they said.

Technically he belongs to her as much as she to him. She might want to remind him that she doesn't share well, if at all.

Please remind her that she does have a say in this.

Does she want him to continue this online play or stop?
As much as I love playing in the dungeon and writing story lines, if my hubby/master said no, then I would stop for him.

Taking/meeting the new girl - in person and as a sub? Well that's a bit much to comprehend or stomach if she wants to keep him to herself.

Grrr! Go with your gut on this one.