Brain Weasels: Jargon That Does Double Dutybrain weasels.
The term itself is needed. It describes a specific group of feelings or reactions that aren't always grouped together. By grouping them together in this particular way, it's easier to identify the root causes of the reaction or feeling and address it directly.
Second: It serves as a kind of safeword.
A safeword is "a word serving as a prearranged and unambiguous signal to end an activity". The activity here are the negative feelings and reactions. And by being a prearranged label, it can cut through whatever drama is going on in the moment and invoke that calmer time. It's a way of bringing someone out of their emotional fugue and back to clarity for a moment.
And it does all that without (linguistically) laying blame.
Brain weasels, linguistically, are their own entities. By naming them as something other than your sweetie, you've managed to address the problematic behavior without actually blaming the person. This allows the person doing the behavior to address the behavior themselves without having to worry about defending their ego.