Let's face it: Keisha goes above and beyond for a high school girlfriend. She sticks by Andy through tough times, even though he's dealing with some exceptionally dark stuff. And Andy recognizes this. He admits:
If it hadn't been for Keisha, I mighta really gotten depressed. After the accident, Keisha was always there. She came to the hospital, to the funeral, to the trial. She was the only one I could cry in front of and not be embarrassed. (17.20)
You getting it? Keisha's really selfless when it comes to Andy. She understands that he has to let all his emotions out before he can be okay, so she patiently listens to his confusing thoughts and ideas about death, even when she doesn't understand them. Through her actions, it's clear that Keisha's as compassionate, patient, and kind as they come.
But after dealing with Andy's mood swings for a few months, Keisha starts to get sick of him, especially because she has tests to study for and colleges to apply to—you know, a life to tend to. So eventually, she ends their relationship. After all, Andy relies on her—day and night—for a long time, without really being there for her. In fact, at one point Andy snaps at her for needing to study. And after all the support she's shown him, it's really not cool that he can't get behind her need for a little time to invest in her own life.
Despite breaking up with him, though, Andy's death hits Keisha hard. After months of being by his side, she doesn't come to the phone one time, and then Andy feels like he has nothing left to live for. Talk about pressure, right? She writes a letter to him after he's gone, explaining her feelings:
You can't be dead. But I went to your funeral. I felt your coffin. It was warm and woody, but you couldn't have been in it. I wanted to open it, to knock and call out your name, but I didn't dare. I went to the cemetery. I kept thinking, Everybody here is dead… they're all dead! Thousands and thousands of dead people—people who would never come back. And then I really did call out your name, and I finally cried. I wept for you—because you weren't supposed to be with all these dead people, because you can't, you just can't be dead. (44.14)
Notice the shock that Keisha's going through. She's in denial about Andy's death because she doesn't want it to be true. So though Andy didn't understand or recognize it while he was alive, Keisha really cares about him, and has all along. Here's hoping she doesn't carry around as much guilt for Andy's death as he did for Robbie's.