Nah--to young teens, she'd look like somebody's grandma.
The people who tell Corissa she looks younger than she is are all other women--and women lie to each other all the fucking time.
Sometimes it's malicious, but usually it's part of a culture of "niceness." That "niceness" has always been there, but it's grown immensely worse since the '80s, with the birth of the self-esteem movement, and an ever-increasing push in advertising and self-help circles to see every woman as "beautiful."
Now, it's obvious that not every woman is beautiful, and if second-wave feminism should have taught us anything it's that a woman doesn't have to be beautiful to be a worthy, accomplished, valuable human being. But that wasn't going to sell Dove beauty products, or Glamour Shots sessions, or "makeover" shows, or myriad other products and services, so through the power of advertising, we're now supposed to believe that every woman is beautiful, even if she obviously isn't, and that you're doing a great thing by affirming that she is.
Telling another woman that she's pretty, or looks amazing, when actually she looks like warmed-over shit in a leaky Walmart bag, isn't actually being kind and supportive--but it allows the person saying it to feel like she is, and if she does it on social media, others get to see how kind and supportive she is. There is a lot of egotism behind the giving of unwarranted compliments, even if the giver herself can't see or admit to it.
I see this all the fucking time in various sewing groups. Whenever a fat woman posts a pic of her latest garment, the rush to tell her how beautiful she looks is on. If it's skimpy, and shows a lot of skin, add "brave" to beautiful, with commenters telling her how they wish they had her confidence. Now, the garment might actually fit her, and be obviously well-made, but scarcely anybody points that out; it's still just one big, mad rush to tell her she's beautiful.
So is it any wonder that Corissa--fat, gravel-faced, alarmingly unhealthy-looking, and rapidly-aging Corissa--gets told she looks so youthful and lovely?