What has the weather been like? When we get a nice, springlike day after our 0 degree weather the goats go nuts, they are really wild and rambunctious. Although they know better than to butt me, ever. But there is definitely a behavior change like that. But I bet she could be in heat, too. Is she wagging her tail a lot more than usual? I agree that you should discipline her however you decide to. If she gets away with headbutting you while she's in heat, or whatever is going on now, she will get worse and think it's an acceptable behavior. That's one thing I have never let my goats even consider. What is easiest is to head them off when they look at you funny. My goats have this certian look they get if they are thinking about headbutting. That is when they get the tap or the spray bottle. Once they start butting it is usually harder to manage.