I'm a Gen Xer who raised 3 millennials. I'm also a former elite-level gymnast. And I applaud you for doing the right thing.
You're not raising a quitter. You're raising a human. She tried it. She didn't like it. It wasn't for her. That's part of life. It's part of growing up, to be free to try anything and to make a choice.
The fact that she was able to come to you is a credit.
Way back, when my kids were young, I let them try everything. We did baseball, track, skateboarding, violin, video making, music, basketball, art lessons, and goodness knows what else. Some stuck, some didn't. That's the beauty of being a kid, trying stuff.