I'm sorry you're going through this with Marcy. It sounds like you have both been through a lot this week.
A foreign body surgery can go one of many ways. The typical path is surgery, followed by ~ 12 hours of recovery and then they typically eat within 24 hours of surgery and they go home. That would be ~ 50%.
Another 30% will have a slower recovery and may take 24-48 hours before they get their appetite back.
The last 20% can be difficult. Some will continue to vomit or regurgitate due to esophagitis or irritation in the GI tract. These dogs are usually the ones that have part of the intestinal tract removed or they had been vomiting for 3+ days before they went to surgery.
The more difficult cases I like to put a naso-gastric (NG) tube in and start trickle feeding a liquid diet. This helps to get calories down to the gut and get it moving again. I find that it also helps that post-op vomiting/ regurgitation that we sometimes see.
I wouldn't worry too much at this point. It's not the norm, but it's definitely not completely unexpected. I would ask about putting in a tube and see if they like to go that route at the hospital she's at. Some are more comfortable than others with this assisted nutrition.
I hope this helps, let me know if you have any other questions.