For sure. Don't be a dick is a pretty good strategy. However, I didn't get the impression that was his intent though: "I laughed along with her joke until, with a shock, we both realized that I was actually laughing at her actual plan".

Right. I was neither being "frank" nor intentionally laughing at her plan. She was smiling, and I thought she was kidding. I was smiling, and she apparently thought I was approving. Suddenly, we both realized we were wrong. Oops.

At that point, the damage was done. I tried to explain why her approach of changing N things simultaneously wasn't more efficient than changing N things sequentially because of the combinatorial explosion of interactions, but she wasn't technical enough to understand what I meant by that, which made her angrier, and when I suggested an approach that would give us a temporary "Plan B" just in case we "ended up a couple of weeks late", she declared me "unsupportive" and ended the meeting.

Holy shit dude, living this now. The pain in terms of support and phantom, impossible to reproduce errors will go on for years.