小二来碗大姨妈
[xiăo èr lái wăn dà yí mā]
Note that this nickname contains rather vulgar elements and is less formal. Here “大姨妈” humorously refers to menstruation. The overall phrase playfully borrows from restaurant serving context and uses colloquial Chinese slang to refer in jest to the menstrual cycle, possibly implying irritability or discomfort associated with the period.