I'm a little concerned because in the picture of the fish, he's got his fins held close to his body. That can bee a sign of poor water quality, and in a one gallon bowl, ammonia can build up really quickly and make fish very sick, especially if they're fed too much.
I know she said not to change the water, but if the fish starts to look lethargic/sick I'd go to the pet store or Wallmart and get dechlorinator drops, then change that water with fresh warm water and dechlorinate it that way. If he starts getting sick, I'd change most of the water twice a day until he perks up again.
Just a head's up. It's tough to manage water quality in a one gallon bowl.