The reason Kelly is called "skinny" and constantly compared to Beyonce is because of her own incessant blathering on about Beyonce's being a "brick house" and wanting Beyonce's thighs. Why do you think she's super muscular now? huh? Naturally thin girls lift weights to create curves.
As for Kelly having a boob job...of course she did. And, she had a nose job, like Beyonce (who's also rumored to regularly have laser lipo on her midsection when her weight is up), Solange, LeTavia, and LeToya.
As for Rihanna being "as skinny as Kelly," no... Rihanna's legs are large and shapely, and though she doesn't have a donkey ***, she has more of a European fuller figure.
Also, people *** think that being "thick" is this or that... Usually the word evokes the same mental images: a girl with a donkey *** or a one who is overweight and merely calling herself thick. It's not true. "Thick" is as varied a thing as "tall" or "***". For instance, Tichina Arnold was a muscular thick girl with a bubble *** (what Kelly would be with all that definition if she were naturally inclined to have a big ***); Trina is a pear shape, a larger lower body but more gaunt torso; Delicious is another pear, but a more fleshy, exaggerated one, who's donkey *** and big thighs are slightly more proportionate to her average sized torso; Mya is a combination of the pear and muscular physiques, with stout, hard legs that seemed skewed when set against her firm mid-section; Ashanti is also a combination of the pear and muscular physiques, however she has more of a dancer's body: solid, bulky legs and an extremely flat mid-section; Rihanna, however, gets us closer to the coke-bottle, with real-life Barbie legs, thick and shapely that give her a curvy physique; and, finally, BEYONCE, the natural coke-bottle shape, the BEST variation of "thick".
So, that's that...being "thick" isn't as simple as either "fat" or "on your way to fat". That's a lie. There's a beautiful array of shapes and sizes...