Well...my hamster doesnt want his treat when he is too excited. So - it might be that she likes the ball so much that she is too excited to eat! If she runs around in her ball and you think she is comfortable in it, it might be that.
Second option - she hates the ball, and feels disoriented and not good in it, so she is so eager to get out of it that she just ignores the food.
So i think you should pay attention if she wants to go in it on her own, and if yes, then she is just happy. If she avoids it, than i think she maybe doesnt like it. Many hamsters dont actually like the ball, and others cant just get enough of it!
Good luck
!