She mentions that she will need to move out
Actually, she doesn't say that she needs to move out...just that she IS moving away.
but NO she never actually explains why she was proposing to move away.
The closest to an explaination he gets (via his doorman passing a message) is...
"Please, tell him I understand if he doesn't want to see me. I'm here just to say I'm sorry, and that my... my life has been unbelievable, since longer than he can imagine,
and I just... I was emotional the other day, and... Now that I realize how
incredibly kind to me he's been, and I... I... I've just been too stupid to accept it, and... I know better now, and... and that's why I want to tell him how sincerely sorry I am."