I didn't care for Brooke at all in S 1-3, but that episode made me feel soooo bad for Brooke. I think she had internalized so much about her insecurities and feelings for Lucas.
Like, I never really thought she cared that much about Lucas, and thought the whole stupid friends with benefits and non exclusive thing was utter crap and she was just being a bratty baby about the whole thing. But I finally got it after that last fight, plus the previous fights where she told Lucas he was supposed to fight for her and not just give up after a little challenge. Lucas wasn't giving her his whole heart, even though is words were nice and sweet and he wrote her letters, his actions showed that his heart wasn't backing up what his words were saying and after that I understood Brooke more and came to like her a lot in S4 and through the rest of the series. While she didn't go through as much crap and pain as Peyton, she had heart heard shredded sooo many times and it was really unfair to Brooke, especially with how much Lucas tried to convinced her and himself that she was what he wanted. God, that scene still makes my heart ache for Brooke, because she deserved sooo much better than the repeat cycle of crap that Lucas put her through. (In case you couldn't tell, I can't stand Lucas S1-4 in regards to the BLP triangle).