If this has begun within the last ~30 hours, it is likely that she is egg bound. Feed for an egg in the area below her vent. If you find one, give her a liquid calcium supplement (or a powdered one mixed with water) one drop at a time, then soak her belly in warm water for 10 minutes or so, dry her off and leave her in a warm, dark place for a few hours.
If it started more than 30 hours ago, she would most likely have died already if she was egg bound. In that case she could have boinked - hit her head on the top of the cage. There is not much you can do about that, apart from keeping her warm and perhaps giving her sugar water every few hours, hoping she gets over it before she starves to death.
If you can't tell if there's an egg, give her the liquid calcium anyway, it won't hurt her. And then keep her warm and calm - a box next to a radiator would do.
Keep us updated on her!
