I think it's just something a lot of CFs have to go through. It's hard growing up having to do all these treatments, and knowing that as you grow up, the probability that even more treatments will be added on. Add normal things people go through growing up and in some twisted way, wanting to choose to make something stop makes sense.
I also found that talking to someone completely outside the situation helped. It was hard talking to my friends, because as much as they wanted to understand, they couldn't, and it would only annoy my when the agreed with me, like they did know. My parents were obviously biased in really only wanting to think about the good the future holds, not the bad.
I hope all of your daughters come to the realization that as suckish a CF life can be, it's worth it to make it as good as it can be.
