Since the pups are only two weeks old I would not take any chances that the Pom and the yorkie mom could get in a fight over the pups. I am really surprised the mom is allowing it. Just because the Pom has never had pups does not mean she does not have motherly instincts. I am sure she is just fascinated by the pups and has not intentions of hurting them but you really never know. I just think it would be wiser to keep her away from them until they are a bit older. I have heard of females that did not have pups letting another momma's pups nurse on them and it will actually bring in their milk. Of course if your pom has never had pups then she should not have any nipples big enough for them to suck on. Believe me though, as soon as they are up and walking around they will try to.
Good luck with your babies.