Is there a common way to translate ajhumma/ajumma into Chinese?
As one can understand from https://en.wikipedia.org/wiki/Ajumma an ajumma (아줌마) is a respectful word for a married or aged married woman, or for any middle-aged or elderly woman, but not a granny, nor a young woman. It is an aunt.

An ajumma is often a housewife, restaurant worker. Ajumma can be used pejoratively.

In Chinese, 阿姨 would fit the description rather well. It is an aunt, or an elderly woman, family nurse or babysitter. Pejoratively, it means concubine.