A few months without food is nothing to worry about. She is getting to be an adult now, and fasts are fairly common. Right now I've got a girl that hasn't eaten more than a couple of small mice in six months. However, weight loss is reason for concern. Parasites could explain both the weight loss and lack of feeding response. A general cat/dog vet can do a fecal float and check for parasites. But if it comes back negative for any bugs or worms, and you are positive she is still losing weight, it may be time to find a herp vet.

I wouldn't be overly concerned about her not defecating. If she's only got one mouse in her system, she may simply be taking her time in releasing it. Try giving her soaks in 85* water that is roughly 1/2" deep. Half an hour is enough time to loosen things up without the water cooling too much and stressing her. Try this twice a week until she goes.