well no, she doesnt really have that perception because it's happened to her her entire life, without even asking for it so she's just learnt to accept that it happens. that's why she's shocked when saiki doesn't attend to her at all. she doesn't ask people to do things for her since they automatically do it because its HER, they wouldnt do it for anyone else.
it has nothing to do with "there are better looking people" (which is highly subjective if youre outside of the show) because she IS the best looking person in their universe
its crazy how so many people mischaractise her when her attitude and personality are so easy to analyse

Teruhashi is really an interesting character. I swear people only hate her just because she knows she's pretty and conceited about it as she rightfully should be. I feel a lot of people dislike her because they know she has the highest chance of being with Saiki out of everyone.