I wish we could've seen how exactly she ended up in the popular girl group considering she's the same ol' Tomoko on the inside.
She might have pulled a Himouto, albert shittier and probably barely.
The omega of the popular girls on the outside, same old filthy mojo on the inside. Also, she was probably approached by Asuka and they were actually in the same class during their first year (Asuka didn't show up until the 2nd or 3rd year.)