Not that this has much bearing, but ANY woman would only be exercising common sense locking the door behind her, especially when alone. I was taught to do this growing up and do this still today and we live out in the country. When I was single living in the city...it was habit to lock my house door as soon as I closed it (too many women are attacked as a result of not doing that...that's just simple fact, I'd rather protect myself than defend myself.) I also still today, lock my car door before I close it....in addition I check the backseat and survey the undercarriage everytime before I get in, I also keep my keys between my fingers...just in case, that doesn't make me OCD right? Just cautious, aware, somewhat prepared, and smart.
I tend towards anxiety issues with your W as well, which in my mind could also explain her actions appearing as preparation for a D. "If" she feels that's the direction YOU are headed the anxiety of what's to come could lead her to make preparations. I don't know...just throwing that out there.
My understanding of people with OCD leads me to believe that people who suffer with this have routines that they MUST complete in order to function, and those routines tend to be very repetitive in nature, not simply done one time. You know....having to count how many times someone washes their hands, turns on/off a light, walks around the house and checks locks....different things like that. I'm not all that well informed on OCD, but that is my understanding of it.
