My mother's endoscopy successfully removed the remaining gallstone and she's back in her hospital room, awake and relatively alert. Barring complications, she's on track to be home from the hospital tomorrow. Thanks to everyone who kept my mom in your thoughts and prayers.
Update to the update:
Well, it's going to be Friday before my mom comes home. She failed her first solid food test this morning (promptly threw up), so they want to let her have the rest of today to get her stomach used to eating again. However, other than that, she's doing well, and when she's not drugged up on the anti-pain/anti-nausea stuff, she sounds more and more like her old self.