The invitation came from the co-workers. They all hang out together, and it was as "Hey, Mrs. Choc., come out with us on Wednesday for Joe's 21st, it'll be fun." kinda thing.
I do think it put my D18 in a weird spot, tho, but if a F18 dates a M21, there's going to be a few age-related weird spots, and she'd best get used to it.
