I think this was the episode where Clay really let Hannah down. With 20/20 hindsight, he should perhaps have stayed with her at the party, but its somewhat to fault him for obeying her clearly expressed wishes. He also should have talked to her when she approached him and he accused her of making everything about her. But at that point, Jeff's death and Clay's hurt and confusion over being rejected at the party were still very fresh.
However, as I understand it, Hannah picked up her check from the Crestmont about three weeks after Jessica's party. During that encounter, Clay was very cold towards her, treating her, at best, as a casual business associate. Both actors were very good in the scene--Clay's indifference and Hannah's wish to engage him and disappointment when he gave her nothing back were both very clear. Go back and look at how fast she spun around when he called her back. It had to be crushing for her discover he only wanted to tell her to return her uniform.
At that point, I think Hannah was fairly desperate to find someone who cared for her enough to put themselves out for her. I don't think she needed any grand profession of love from Clay, but she did need to know he cared and would stand by her, Instead, she got nothing but indifference. I think that if she had believed Clay cared about her, she might have called him after the scene with her parents rather than wondering over to Bryce's or, if not, might have called him after the rape.
In the second season Zack said that shame burns. I think that if Clay ever looks back on this conversation, he should feel a good bit of shame that burns. His treatment of Hannah was far short of what she had the right to expect from a friend, much less from someone who professed to love her