I've always used the phrase "needed help" also. When I was pregnant with my son i told him that most babies are born between the mommy's legs, and she pushes them out, like when we go to the bathroom. That I tried and tired to push him out at home, but then I decided he was a little too stuck and I needed the DR to help me, so the DR helped me get him out of my belly by making a hole. I told him I was going to try the same with his sister-- to push her out in our home, but if I needed some help then I would go to the hospital and he could come visit me the next day and push me up and down the hospital bed (seriously, this broke them tension SO WELL when he met his sister).
I'll tell her the same. Most babies come out between your legs when you push, but sometimes you need some extra help and then they make a hole in your belly to help the baby come out safely. I don't think that will make her think she can't do it. My mom always told me birth horror stories, and I was still a HB advocate.