Would you address someone this way? Lots of people do, and I've witnessed lots of the so-addressed not bat an eye (including my mother-in-law). And now there's a new Korean restaurant in Chinatown that's appropriated the term, pairing it with a cutesy cartoon logo of what appears to be very unajumma-like little girl in a traditional hanbok, serving up something in a pot.
Apart from that, Ahjoomah's Apron is significant for the fact that it's the only Korean restaurant in Chinatown
(perhaps the only one on the south side), and as such it adopts a tone that most Korean restaurants that operate outside the orbit of a significant population of Koreans adopt. It operates under the assumption that most people will have no idea what they're doing when they walk in. So the walls of the bright, modern rehauling of the old Emerald City feature blow-up English texts on the basics of Korean food if, say, you need a history lesson on kimchi or bulgogi or pajeon.
The half-dozen gratis panchan—kimchi, fish cakes, black beans, soy-glazed potatoes, and pickled radish—seem a little skimpy, but they're fresh and continually replenished by a superfriendly and attentive staff that includes at least one very sweet ajumma. It's starter-kit Korean, but still a welcome addition to Chinatown's ever-diversifying options.