Background - Swam a couple of years year-round as a youth (11-12), summer swim team from 9-18, one year of high school swimming. D-1 Runner.
Let her decide what she wants to do. If she doesn't enjoy it, she will ultimately quit. She's in Fifth Grade, right? Try to make sure she is doing something weight bearing (running, soccer, basketball, lacrosse, field hockey, etc.) outside of swimming. Make it fun! Just get her moving on land.
Swimming is great aerobic prep for running, from my experience. Every day was like low-end V02 Max work, without the pounding. Kick sets kept hips and quads powerful, glutes and core engaged. If I was running and swimming, I always felt "tighter" (in a good way), while running. However, you will be tired, and nothing in the water translates to fast running - you still have to work at speed. I did notice that I could keep running volume relatively moderate and still maintain good fitness if I was swimming at least 3 times a week (3,000 + meters a day).
Finally, swimming does prepare you to work! While you cannot get anywhere near max. heartrate because of the water and horizontal position, doing hard swim sets with 5-10 seconds rest will make the long rests of track work seem easy, at first...
Good luck - keep her moving!