1.
First, when Blair read Serena the letter she wrote her when she left for boarding school without any explanation:
2.
When Eric came out to Serena:
3.
When Dan and Serena realized they needed to finally break up, and they shared one last kiss in the elevator:
4.
When Blair couldn't accept her breakup with Nate:
5.
When Chuck considered suicide because he thought his father was dead:
6.
When Blair told Jenny nobody loves her:
7.
When Nate turned his dad in for using drugs:
8.
When Chuck lied and told Blair he didn't love her back:
9.
When Blair had a miscarriage:
10.
When Blair told Chuck she was done fighting for him:
11.
When Eric told Blair he had tried to kill himself:
12.
When Serena saw Dan move on quickly after their breakup:
13.
When Nate stayed in the hospital all night with Serena after she was in a car accident:
14.
When Chuck slept with Jenny because he thought Blair didn't love him anymore:
15.
When Serena and Blair's prom didn't go as planned, so they ended the night together, just the two of them:
16.
When Blair told Chuck she never thought he would hurt her like this:
17.
When Serena broke up with Nate:
18.
And finally, when Blair told Serena there was nothing she could ever do to make her let go of their friendship:
