My big billy comes in at night looking like that. Once they lie down, stop eating, and chew the cud, it gradually goes down. If they gorge too much rich grass, it can cause wind, and their bellies go big and rock hard. When this happens, I rub the big bulge until they burp (sorry!) bringing the wind up. Its like trapped wind - once thats done, they are much better!! Unless your goat looks uncomfortable, she should be ok. I do try and bring mine off the grass during the day a bit, to try and stop them eating too much. It can be very rich and green.