I've noticed recently that my wife frequently cuts people off and interrupts in conversations. I've seen her do it to more people than just me, but by virtue of being around her a lot notice it a lot more.

Should I consider this a form of shit test, or am I overreacting when it frustrates me?

My father was very old-world in his upbringing of me, and when I was young instilled in me that it was very rude, impolite and disrespectful to interrupt someone. Consequently when my wife interrupts me I can't help but view it as a lack of respect.

Before becoming fully RP-aware, I handled it by telling her straight up that I didn't appreciate that she interrupted me and saw it as rude and a lack of respect. She still does it, albeit less frequently and often will catch herself and apologize.

Am I making something out of nothing with this, or is it a shit test that I need to better address?

As an interesting aside, she once said that she interrupts me because I speak slowly or take pauses... two things I've intentionally started doing as part of my self-improvement.