你美的像你大姨妈一样
[nĭ mĕi de xiàng nĭ dà yí mā yī yàng]
The term ‘Dàyímā’ literally means ‘maternal aunt’ but is commonly used as a euphemism for ‘period’ or menstruation in China. Thus, it humorously translates to 'You're beautiful just like your period', implying the person is not as beautiful as they think they are - in Chinese culture, getting one's period isn't usually regarded as glamorous, making this a sarcastic insult.