Young feet are probably fine in flip flops, just don't get old and you will all be fine!
I can wear them all day. Last year we made Rope drop at DHS stayed until park closed and walked back to BW and I had no problems.I do not blame her. I hate crocs. I always wear Teva Mush and I love them. Just make sure you get the Original Tiva Mush and not the Teva Mush II. Sadly there are only two choices to choose from right now because they just brought the original Teva Mush back after much complaining about Teva Mush II. If I am not in my Teva Mush then I have on Tennis Shoes.
http://www.amazon.com/Teva-Original...ERFE/ref=sr_1_1?ie=UTF8&qid=1334676948&sr=8-1
I wouldn't be caught dead in those things....sorry, I understand your tween's plight. Tell her to bring worn in sneakers. I wear flip flops (gasp!) some days too, especially when doing a half day at a park.
I am heading quickly toward 50 and I still love my Teva Mush Flip FlopsI can wear them all day. Last year we made Rope drop at DHS stayed until park closed and walked back to BW and I had no problems.

)I wear Easy Spirit shoes, but the people who are saying Crocs are ugly probably haven't looked at the variety of styles lately.I agree! Crocs are UGLY, IMO. Blech! I'd get her a good pair of walking sandals (Keen, Teva, Ryka) or walking shoes (Ryka, Adidas, New Balance) -- they will be much more attractive which will make her happy and will be just as comfortable.