A.K.
I started using tampons when I was 12. I was on color guard and our uniforms had short skirts like the cheerleaders. The thought of wearing a bulky pad with those little bloomers was mortifying so my mom let me use tampons. She read over the insert with me and talked to me about TSS. She also got me a little tube of KY to make them easier to insert (though with the newer plastic applicators I don’t know if this is really necessary.)
Since your daughter swims I’m sure she’s having many of the same feelings I did. I would let her use them and let her try out a few different brands so she can decide which ones she likes. I had to use tampex until I went to college and they were not the right fit for my body.