M.B.
First off there's nothing wrong with her only wanting the swings. She's got her favorite and that's it. You could find a park with no swings to take her to occasionally. If you just want her to run and play with a ball you can find a place away from sight of swings and play there and then take her over just before you are about to leave the park and let her swing on the swings. Also, other children are a great motivator. So if she has a friend around her age or even older who you can have a playdate with then she might be more willing to try what she's doing. I wouldn't push it too much though.