Your nest box is 5 feet up? That's pretty high - they might (MIGHT!) survive a fall or a jump down, but certainly couldn't get back up! I don't think that is a good arrangement at all. At the very least, they initially need a nest close to the ground. It's a little late to be telling you this, but I always separate my broody and her clutch, as soon as it's apparent that she's serious, in a separate "feed room" in my coop, and keep them there until the chicks are around 7-10 days old, then let them mingle with my flock of 25 hens some during the day, but continue to keep them separate at night until they are fully feathered and their mama doesn't really want to take care of(ie: sleep with) them any more. I guess what I would do, if I were you, is go in during the night and take her and her nest and clutch and fix them up in a safe, separate area within the coop or somewhere, and hope for the best.