AIO gf doesn't want to remind plumber she's dating me

The plumber is coming by this morning. He's been to our house before and last time we had an awkward hello before I went back to my office.

This time, my girlfriend asked me to not come out while he is here. When I asked why she said "because he used to want to date me and I don't want to remind him that you're my partner."

I know they aren't having sex or anything but I still felt like it was wrong to consciously try and hide our relationship from another interested man.

I told her this and she said I was insecure before getting mad and telling me I'm overreacting. Am I?