If there isn't any medical reason for having smaller thighs and it is just for appearance, then I would just explain how skinny legs aren't really better looking, the opposite in many cases.
yeah but you know because of her build and because she is short, her large thighs don't look very well, she looks overweight, sure she has fat on them, which she would lose, but she wouldn't much like to increase her muscle mass in the process you know

large thighs look good on a taller slimmer build but for her its not so.
her goal more specifically is to thin down as much as possible (while staying healthy of course), as in lose excess fat in a healthy manner, and limiting the amount of mass she would gain in her legs. (so stuff like squats are definitely out of the picture)
so yeah .. loose weight and regain what stamina she lost.
i told her if she loses the excess fat then she'd look okay.
her legs are very strong, back in the day nobody could beat her at the 50m sprint.
i was thinking of getting her to do cardio which also involves upper body as much as possible, since she doesn't gain muscle in her upper body as easy as in her legs, and even if she would add decent amount it would be beneficial to her look since she's not all that broad in upper body.
ps: she is fairly knowledgeable about the subject, and she knows a lot about nutrition all she needs is a good source to base her nutrition plan off of,