Sara knew she was a mentally ill person, that's why she left Vegas, back to Berkeley. Earlier in her life, she had gone to a therapist there to help resolve issues from her childhood. Therapy had worked then, she wasn't sure it would now, but she had to try.
Grissom knew she was troubled, but didn't know how to help her. He thought maybe time would heal her post traumatic stress. He was wrong, but since she had gone, he was there for her every weekend.
Between therapy and Grissom, Sara was getting better, then Warrick died.