本姑娘自然熟
[bĕn gū niáng zì rán shú]
本姑娘 refers to 'this young lady/girl', 自然熟 (zìrán shú) means 'naturally ripe'. In northern China dialect, especially Beijing region, it’s humorously meant when referring girls who need to be pursued to show themselves/attraction, which adds self-confidence or casual charm.