I agree with people in little light contact during the term... Hormones are kinda crazy.. you really wouldnt want to work her up!! so, she needs to be dealt, firmly yet gently that she IS NOT gonna be involved in ANY part of the child(ren)'s life/lives.. nowhere does it say in the contract that you have to let her, right??
Besides you are right, she is not only doing this out of the generosity of her heart.. she is being paid.. so really, u wanting not to be involved in her mood changes, doesn't make you a jerk!
And that in NO WAY says that you're not cut out to be a dad! Also look at it this way, if you keep in touch with her, even minimally, you would be involved in this period of your kid(s)' lives... acc to some of the parents i know, it can actually be fum.. to know when the baby kicked, and when it gave her spasms.. etc.. so..
U just gotta make sure she has no allusions over the fact that she's gonna be involved in this kid's life in ANY way, whatsoever.. if that's how you want it, that's what will happen..
like i said earlier, i think you're gonna be a wonderful dad! :) so... dont ever question that!! and you'll be good to go..