Forum:Cass' quest won't work?

I killed the Van Graffs for Elder Hardin, and killed McLafferly (after doing her quests) Because i hated her. When I went to see Cass (not yet a companion) she commented like it was the end of her quest, and I completed it, but didn't get her perk. When I did recruit her she told me to investigate the caravans but when she told me to kill the graffs and McLaffery, no matter what I did I couldn't get her to comment on the death. Any help?