Hmmmmm... How about when she starts venting about work, you could say...
"You know, we just spent ten hours in that hell hole... Let's talk about something else..."
"Hey, how about them Rangers, huh? Man, they are killing me!"
"Not to change the subject, but I just tied this great recipe for cannoli dip! The stuff rocks! Want to try some?"
Boundaries can be a bugger. It is hard to set a limit without coming across in a negative way. Being frustrated makes it harder.
BTW... quit counting the days. It is not a proactive thing.
What really makes redirecting the conversation so difficult is that I use to do that before BD. She always tended to see the negative and made it worse by dwelling on it. I would try to help her see the positives and, failing that, change the conversation. I am more of a work to live kind of person, but she seems to have become someone who doesn't have an identity outside of work. Her self worth appears to be entirely based on work. As she has a very low opinion of work, and her job in particular, she has even worse self esteem issues than normal. Tell me how do I change work related conversations without all of the apparent pitfalls?
As for counting, I am not actively doing it on a day to day basis. Somedays I just can't believe how long this has been going on. On those days, I just use a handy counting app. I get what you are saying, though. It isn't helpful and doesn't change anything.