She is probably an excellent sailor, and probably can cope with most expected equipment failures. I don't know that much about sailing, but I didn't think sheer brawn made that much of a difference. She could be as strong and capable as a petite adult woman.

But - and I say this as a mother of a 12 yr old boy, not girl - I really cannot see any 13-yr. old having the imagination, and resourcefulness, and the understanding of her own limitations, and the ability to judge other peoples intentions - to safely handle many other, unexpected situations. When I was 13 I was Superwoman. Nobody could tell me what I could or couldn't do, because I could do everything. I wildly overestimated my own abilities, and conveniently ignored any results to the contrary. Isn't this why kids aren't allowed to vote, or marry, or hold jobs?