How can you tell when you're ready to talk about what happened? How can you tell when you're not ready?

I'm still on the fence with doing trauma work with my therapist. She checks in with me weekly and asks if I feel like I'm ready to talk about it. She says she thinks I am ready, but I don't know if I am.

How can you tell when you're ready? What are some signs that I should look for to know that I'm ready? Are there things I should be paying attention to to know if I'm not quite ready yet?