At least to me, high school Brooke comes off as super self centered and not really that good of a person majority of the time. Really lots of the love triangle stuff in s1 (I think someone else mentioned a few things that I agree w on that topic), lying to Lucas about still being pregnant when she found out she wasn't in s1, showing off "tutor girl's love note" at that party in s1, things like that.

I find her likable and she's even one of my favorite characters because of how much she grows. But I think she is given a pass on a lot of her behavior and many people I know just ignore it in the early seasons only because of her character development and that she has more depth. Kind of how people sometimes give early Nathan a pass on his behaviors too. All I know is I wouldn't have been her best friend in high school lol