Honestly this all sounds like it is about you-
The feelings you experienced in her presence.
The comparisons you have made between you.
The assumptions you have made about her life.
The beliefs you have created about how she thinks and feels, her intentions in life.
She is allowed to have been pretty and popular without this being any crime or having wronged you.
Ok, maybe she could have been more aware of her advantages in life, but seriously, who has this insight as a teenager/YA?
Or did you leave out her actual crimes in your OP -there's was nothing objectively wrong described.
My guess is that your own SE issues created a narrative in your head that has made you behave in a standoffish or other unpleasant way such that when you made the friend request she wouldn't have understood why you would. Certainly, no-one here can understand why you did.
My aunt created this narrative with a neighbour. "thinks she's better than me" "looks down on me" "so popular, don't know why" comments about weight (being slim) and appearance etc. The way my aunt spoke it was like there was some sort of vendetta/rivalry. Except I knew the woman, she was a friend's mum. A nice person who barely realised my aunt existed. It was always all in my aunt's own head, she created the whole narrative. Created her own suffering and denied herself the chance of a friendly relationship. Years and years...and years...later, in her 70s, my aunt mentioned the woman and made a throw away comment "think I imagined we were in a competition or something". So I guess she finally realised.
Comparison really is the thief of joy.
And less cliche: If you are tormented by strong feelings that persist over a long time, it's vastly more likely to be of your own making than to truly come from someone else.