The "stone" is called a urate. It's just hardened urine.. The "anus" is the vent..

She will be fine. Next time she decides to go off feed for awhile don't give her large frequent meals once she starts again. Give her meals that are no more than the same size around as her widest part and preferably a bit smaller than that. Plus wait a week between feedings.

It can take their digestive systems to get back into the swing of things after they've not eaten in awhile so you want to start them off easy.