My 10-year-old self might be disappointed that I didn't grow up to marry Luke Skywalker, Superman (Christopher Reeve!!), or the Christian camp counselor I had a huge crush on during the summers. He was so good-looking that he could have easily been part of a famous boy band (and he liked to sing, so it was fitting.)
I would tell her though, that as you get older, you find out that even your biggest heroes are still human, and that years later, she will run into that gorgeous camp counselor again on social media. This time, he'd be a middle-aged married dad of all boys who sings in a barbershop quartet, and she would see how much life (and her perspective of it) can change over time.
I know she'd be disappointed that I'm not married with a family, but I'd tell her that no matter where God takes me, I've never left her behind, and hopefully, I never will.