It could be the rich grass, or the hot weather, or a comibination of both. Or even something she ate, has upset her tummy. If she is still eating, she cannot be feeling too ill. Is she drinking water? You must try and get some water down her, thats the important thing to stop her dehydrating. As much as she can drink, the more the better. Is there any way you can keep her off the grass, and just put her on hay, with water of course. Usually, that dries a goat up.