Lots of good information here. I'll add what I've learned over the past few months.
If she puffs up and growls at you then she is broody. I didn't see any mention of a rooster so if you don't have one then you'll need to break the hen from her broody cycle. We put one of ours that was doing this into a small dog cage with a wire bottom with the cage raised off the ground a few inches so that the hen couldn't generate a bunch of body heat and we left her there for a couple of days. Yes she had food and water in there with her. That was done from advice I gathered here on the forums. I honestly have no idea why it worked but it did.
Now if you have a rooster and want some chicks then you're in a prime position here. You'll need to separate the broody hen into her own little nesting area. Either build a smaller coop (what I did) or go the easy route and get a small dog crate off of Craigslist or borrow one. Put some fencing around the Broody Camp and ensure she has her own water and feed. Before you move the hen into her area take a pencil and mark each egg that she has under her with a that days date. We did this when our last two went broody but we dated them the days they were laid so that we knew when they were supposed to hatch. Then move the hen and the eggs you want her to have out to the camp and let her be for the next month.
Hope some of that helps.