Lark definitely pushed Katy into what happened. It was sort of the "straw that broke the camels back" - but a lot of it had to do with the fact that this thing happened...and she didn't really know what happened because she basically forced herself to forget it. Happens a lot with tramua victims. What you saw as readers is all that Katy remembers from that night until waking up in the hospital. She doesn't even really remember Mike and Holli and Marsha coming over to her house the next day and finding her (like Mike mentions to Kevin earlier in the story).
And the connection between Greg and her work slipping - non-existant. He's been the one really good thing she's had in her life in a long time. You saw him say "I thought you were cutting back?" and she laughed...she's been hiding how much she's been deteriorating from him when he visits. Which is why she attempted to clean on Thursday night when she got home (not that she was in really any shape to do so at that point). However, Katy's also reaching a point where she's scared of what she feels. And when Katy gets scared she runs.
And the connection between Greg and her work slipping - non-existant. He's been the one really good thing she's had in her life in a long time. You saw him say "I thought you were cutting back?" and she laughed...she's been hiding how much she's been deteriorating from him when he visits. Which is why she attempted to clean on Thursday night when she got home (not that she was in really any shape to do so at that point). However, Katy's also reaching a point where she's scared of what she feels. And when Katy gets scared she runs.