闺蜜的别名叫小三
[guī mì de bié míng jiào xiăo sān]
In modern context, this implies a rather cynical view towards friendship among women ('guimi', female friends). It hints at betrayal within female friendships, suggesting sometimes these trusted confidantes (the term 'guimi' implies close, trusting female relationships) become 'xiaosan,' which is a colloquial term used in Chinese-speaking regions to describe a homewrecker/third party in an otherwise stable marriage or relationship.