Being Mixed in California Has Made Me Soft

Since moving to California in the fall, no one has asked me what my background/heritage/ethnicity/parental birthplace is. It's been nice and I didn't miss it. Yesterday, my "It's been 160 days since our last questioning" sign was erased and put back to zero.
I was with my boyfriend, his friend and the friend's fiancee. We were having a great day. All of us are people of color and I wasn't thinking anything about it - it's nice to just be comfortable with the people around you. Out of the blue, the fiancee asks me about my background. It felt like someone slammed on the brakes of my good time. Suddenly, I was aware of the fact that I'm obviously different. I went from assuming I was part of the group to feeling like an outsider. And, because it's been so long since somebody asked or I thought about being mixed, I sort of stumbled over my answer. No snappy "What do you think I am?" Just, "Ah, well, um, huh, yeah, that came out of nowhere, uh, yeah."
It turns out she is mixed also - Asian and White. I assumed she was simply Asian, but maybe she is often asked about her heritage and didn't think I would find it disconcerting when she asked.
The upside is that I knew there wasn't anything malicious behind it and so I recovered pretty well. I still like her as much as I like anyone after one meeting (I'm slow to call someone a friend) and look forward to us reveling in the comfort of being four people of color on the town sometime soon.