To vent your spleen means to voice one's anger, but the person in the context keeps their anger and frustration to themselves.
Consider the staetement "Barb leaves, you can't deal with it, so you keep your anger and frustration to yourself at her and the company she works for.". Based on this statement, is "Barb leaves, you cant deal with it, so you vent your spleen at her and the company she works for." a true statement? Yes/no/unknown