This has nothing to do with the original comment. I'm not finding anything difficult to grasp. I'm simply saying your friends height has nothing to do with her clothes size.
You said you're friend is thinner than you, but she is a larger size. This isn't possible, bigger size = bigger measurements = larger proportions. She may have more muscle mass/lower fat percentage so may look better, but she is not smaller than you.
All of this has absolutely
nothing to do with her height which is just a coincidence. Tall people do not have more "broad" bone structure, they do not have higher body fat % and they do not have more muscle mass by default. They have the exact same body as smaller people, with a few more inches. Anything else is just an illusion.
Also, does she have proof for this apparently "broad" bone structure? X-rays for example? All I know is it's a nice excuse for being overweight "sorry, I'm big boned"