I agree with pretty much everything that's already been said. Her legs are NICE! Gosh, why would she want thinner legs, hers are great!
I used to feel the same way, I've always had naturally big, muscular legs. I don't weight train mine at all either, instead I'm a speed skater so I do a lot of sprinting on my inline skates. So now (after years of speed skating) they are still muscular but now they are more shapely, I carry less fat on them than before.
I used to complain about my big legs even as a kid (before speed skating) and my dad used to tell me that I just needed to work my upper body to bring it into PROPORTION with my lower body cause genetically I was always gonna have big legs. Low and behold, years later when I got into bodybuilding, I discovered he was SO right! Now even tho I still have what the norm would consider big, muscular legs, they match much better with my upper body, after lifting for about 3 1/2 years now.
I have told one of my speed skating teammates the same thing. She constantly complains about her legs being too big and I tell her, well, unless you want to quit skating and start dieting hard (and even that's no guarantee) you're just going to have big legs, bottom line, end of discussion. So, what you have to do is build up your upper body to MATCH your lower body. I've told her that more than once already but I think she's still too afraid to lift, she's still afraid of getting bulky. So I suppose I will keep having to hear her complain about her big legs. Some people will never learn.
As everyone has said, learn to appreciate and work with what ya got!
I used to always want to be one of those small, petite girls (what WAS I thinking, lol) until I finally woke up one day and realized that even if I dieted down to nothing, I'd STILL never be petite! My genetics are just NOT petite. Rather, I tend towards stockiness (as do both sides of my family, we are farmers of German ancestry), thick bones and I carry more muscle on my frame (always have) than most women. So I finally stopped FIGHTING my genetics and learned to ACCEPT my body just the way it is. Something to keep in mind is that there is NOT just ONE body type that is considered attractive. There are MANY, MANY, different body types out there that are attractive! So go with what ya got!