This is one of those great examples of a T stating something about you that she knows others are experiencing or may be experiencing from you IRL. And your T is right; interrupting does make people feel like you don't want to hear what they have to say. I used to interrupt and talk a lot more than I listened. Over the years, I've made it the other way around. It started with self awareness and was helped by others pointing it out. On some level, you must be aware that your're doing this. I would go a step further than just asking T and suggest that you ask very close friends, family, and loved ones to point it out when you do it too...the ones who love you unconditionally. The more often you have people pointing these moments out, the better it will be for changing the habit.

Also, I think it's more effective to think of adding a new behavior rather than stopping a habit. For instance, say to yourself that you are going to be a better listener rather than saying you are going to stop interrupting. By actively listening more, you will stop thinking so much about what you are going to say/feel like you must say at that moment.