Some things are funny because of the person who says them. Given that she’s an older woman and has been with men, I read it as tongue-in-cheek, a feigned prejudice. I think she’s teasing, enticing you to a little good-natured mock battle-of-the-sexes debate. “Men are not observant? What about women?”
In the original “City Slickers” movie there was a scene where the men are defending baseball to a woman on the trip. Daniel Stern’s character (Phil?) says (words to the effect), “When I was a teenager and my father and I couldn’t talk about anything else, we could still talk about baseball.”
Maybe there’s a partial answer to your overall dilemma in there. Find the common ground you have with the MiL—things you’re both interested in—and make those the “go to” topics when you need them.
Well, not to beat a dead horse (and maybe I’ll just have to settle for having a different opinion on this than most here), but:
With respect to point 5, I’m not in any way trying to say that she was offensive, or that I would be offended, or anything like that. Just that without an appropriately receptive audience her joke is not only unfunny, but doesn’t even hint at funniness. A bad pun might not be funny to you, but you can see the cleverness in the word play, for example.
I also don’t think that every person needs to give a cold shoulder to any joke he or she doesn’t find amusing. I am saying that it’s not the listener’s responsibility to laugh at anything just because it was told to illicit a laugh (or an, “amen to that!”)
One of my roommates and I are Jewish. We make occasional Jew jokes to each other about being stingy with money and other generally negative Jewish stereotypes. They’re funny. They’re not meant in any sincere way at all (which is more than I feel like I can say for most times I hear people complain/joke about the stupid thing that men/women always do). However, I would never bust that sort of joking conversation out when I wasn’t sure that people were in on the fact that I didn’t mean it. If I misjudged and got a cold stare, or silence, or a “that’s really inappropriate,” I wouldn’t assume it was the listener’s fault for not getting it.
I feel like I’m almost turning this into a CS thread on the nature of jokes.