How old is she ?
I don't really see a "fat" snake, and over feeding is something I'm very much against. Overweight Ball Pythons loose that defined, skinny looking neck. Look at the neck in her picture, its quite thin still.
What size food are you feeding every week ?
Ball Pythons are "heavy bodied" snakes. They appear chubby to many other snake species. However, they certainly CAN get overweight, but I don't really see that ? If she can do all the things you said she can do, plus she is doing well, then I wouldn't worry to much about it. If you do give her something to climb on, make sure its not to high. They really aren't very graceful climbers at all and fall off at times. That's when you hear the dull "thump" in the night..LOL.
Give us some more info on age, size of food,etc![]()