I'm glad your sister decided to change her mind regarding the intended use for the camera. The truth is I have NEVER seen what I would consider acceptable action shots from a digicam for indoor sports. Yes, one or two, but if that was going to be a primary purpose for the camera then I think she would be set up for disappointment.
Robbo makes a good suggestion - you'll need all the zoom you can get when shooting softball. So, look into the 12x zoom cameras as your sister will need every bit of that zoom - even if she were on the field. When I shoot softball, I'm using the equivelent of a 480mm zoom lens and I shoot from the field. That is just enough to shoot from the first base line to the third base line with some occasional outfield shots. And that's from the field, not the stands. So, I think for outside sports the superzoom is the way to go.
She'll be able to get some nice shots with one as long as the lighting is good. All of them should have a sports mode on them - she can just use that (as opposed to auto mode).