Long before pregnancy was on my radar, my college roommate (one of the most organized, type A people I've ever met) gave birth to her first child. She told me that she walked into the hospital with a typed-out copy of a birth plan (involving natural delivery, no interventions) to hand out to everyone involved. She left with a C-section and an absolutely perfect baby girl. I'll take that with me always.
Everyone's childbirth experience is different, and it's important to be able to roll with the punches and not panic if things don't go according to plan. Sure, you should have an ideal scenario in mind, and know some of the different paths that your delivery might take. But let her know that whatever happens is A-OK, as long as the end result is a healthy baby (and in turn, a happy mama).