I suggest going. If you get into the habit of canceling appointments this early in the relationship you will continue to tell yourself that it's ok. I have never canceled an appointment with T for avoidance issues and it has enabled me to get myself to some pretty rough sessions. If you are an avoider, and you know you are, don't avoid therapy. You are there to stop avoiding!

Going to the session may be the biggest step you can take next week. And that's ok! It means you're being proactive. If you're able to take another step, maybe tell her that this is a hard week but you're not ready to tell her why. Maybe instead you could have a conversation about why trusting her is hard for you. It may help set the tone for future sessions.

This is hard, but you can do this! She will support you through this rough week even if she doesn't understand why. She's there for you. Best wishes