Hi, the best thing is to starve her, and if you can get her to take a little bit of vegetable matter this will help, but sometimes they can clear just by being starved for a few days. If you have a breeder net to put her in she will still have the same water she is used to circulating but not get access to the food when you feed the other fish. Equally, in a breeder net she can rest away from any potential bully while not feeling 100%. If possible put a piece of a plant in there so she can rest on it.
If I am going away for a short period I do not have anyone feed my fish, I feel they are better off this way than taking a risk. Otherwise I make up small containers, like the type you get for crafts/pills and put the required amount for each tank in there. This ensures the person dealing with the fish does not overfeed, which is a common mistake for anyone who is not a fish person.
Last time I took a tank (it was small) over to a neighbours for a few days, I arrived back to find the water so toxic that a fish was dead and my fighter (Bob) was gasping at the top. I then decided never again. Do not blame your Mum, she would have thought she was doing everything right.
Post a picture if you can, and look at her from above to, making sure it does not turn into dropsy.
Oh, and do a WC if not already, as they maybe some uneaten food in the tank rotting.
Fingers and Fins crossed for you and for her.
