The answer  used to be 42.  Then Fenchurch figured out both, so the universe became more bizarre and inexplicable.  Consequently, the question-answer pair that includes 42 no longer applies.

She mentions that her memories of that event are hazy, so probably at this time she doesn't recall killing him.  She still has her conditioning, so when she meets him again she tries again.  Later she learns what she did.  Just because she doesn't recall it doesn't mean she's won't feel guilty.

Their time lines are generally opposite, but not strictly.  If every time they met it was earlier (i e earlier for the doctor from her perspective, and for her from his) they wouldn't need to compare diaries.

From history's perspective, and from the doctors, she was killing him early.  From her perspective she already has (the events at the lake were when she was still a little girl, though her memories of them were a bit fuzzy.)