I guess the question is how many can you afford or are willing to have. Also and I'm not sure how to ask this but is there some emergent reason she feels the need to do this? if not, then your question might be a moot point for she may outlive her babies. She may also be planning on placing the others, aside from the one you want with other people.
On another note, what an honor. It sure says a lot about you and your character.
