吃个醋都不能名正言顺
[chī gè cù dōu bù néng míng zhèng yán shùn]
Translates as 'can't even eat vinegar on justified grounds', it is actually using sarcasm to describe jealousy (the idiom to ‘eat醋’ here is a wordplay similar to say someone feels envy or green). It suggests feeling jealous but without having legitimate reason.