I really like these small dosages of fluff.
Seeing Nikaidou trying to boost Tadokoros confidence is really nice and shows that she doesn't just project her personal feelings of love onto her, but also cares about Tadokoros own feelings and wants to help her feel better about herself.
Also with the point of whether she was cute before or not, we still read a manga here. The mangaka suggests on a narrative level that she looked gloomy before and fixing up her hair helped a little to improve on that. Most mangakas wouldn't ever actually draw someone as ugly or gloomy as they're suggested to be through the narrative.
I myself am okay with such small divergences between art and narrative, but I can understand if others don't feel that way. There are obviously limits to how much the suspension of disbelief can be strained. In this scenario it still works for me. I can go along with the narrative of Tadokoro appearing gloomy, while she's actually drawn really cute and beautiful.