小三玩得永远是剩货
[xiăo sān wán dé yŏng yuăn shì shèng huò]
The name 'A mistress always ends up with leftovers' suggests an opinionated comment on relationships outside marriage. It reflects the belief that being the 'other woman' or engaging in extramarital affairs leads to nothing valuable but rather remains unimportant or undesirable.