不是白富美装什么卖萌妹
[bù shì bái fù mĕi zhuāng shén me mài méng mèi]
It sarcastically criticizes girls (or women) trying to act cute ('play innocent/act coy') when they are not wealthy, beautiful ('white collar, wealthy, and pretty girls'—often translated from Chinese internet slang referring attractive and affluent ladies).