As long as she stays laying on them. They can't let them get cold. I have never had a broody hen well once or twice they got a little broody but they always gave up. You may as well wait and see!! I wish you luck!
I bet she knew the one she rolled down the ramp wasn't viable. As for the one that got cracked it could have been an accident especially if shes not eating all the other ones. That's disappointing though to find you losing eggs.