how about you just fucking do it yourself you dense little ... AAAAAAAAAHHHH
Tbh, can't really fault her about most of that. There's social pressure, which can be a thing, but also obvious lack of confidence on her part regarding her own image and how cute things would suit her.
But more importantly, I feel the bigger hurdle is her father. From what we saw, she has good reason to worry about his reaction if he found out her love for sweets. Dude basically tried to name her "no sweets allowed !" for fuck sake.
She also working on those issue, mainly the eat sweets thing. That's kind of the whole point of the manga, after all. My main beef (pun intented) regarding that is how they do the whole plate exchange as if nobody would see them stuffing their face with the actual food they're eating. XD
As for the lil sis, I don't see how she can do it herself, beside kidnapping Mito's. XD