Glad you got a giggle out of it!
You're right, eating vinegar is actually the literally translation of feeling jealous.

The phrase comes from a historical story about a Prime minister who was granted a visit from a concubine under the Emperor's wishes. The prime minister's wife was not accepting of this and said she would rather drink poison than see her husband with another woman.
So, the emperor gave her a vial of "poison" which was in-fact filled with vinegar because he was moved by her courage and love. She drank it and survived.
Since then, "吃醋" - eating vinegar is used when referring to someone who is jealous (mostly of their lover).