Her anxiety is definitely born from him not making a move (or him not rejecting her outright) as that chapter makes it clear. She wants to retain a way of not making it weird, so she says it's nothing.
That said, she misinterprets his teasing as rejection of her appearance. Many girls subconsciously (or even consciously) change appearances for their men, but other than health, men aren't so appearance-driven.
I can't say I've seen this exact situation outside of manga, I've seen pieces of this in my grade school days. My fiancé's little sister is a big tsundere like this, thought she keeps trying to get our advice and never leaves us alone, so MMC's plight is very relatable here lol