Is it necessary to tell car insurance company?

I was pulling in my parents driveway and someone related to family through marriage was pulling out. She was putting on her seat belt and didn't see me. There's a turn off the driveway and I tried to quickly pull into it to avoid hitting her head on. I didn't quite clear a tree and it damaged my car. She pulled away and I'm not sure if she even knew I hit the tree. There's a lot of tension already and I don't want to ignite disputes with relatives by blaming the collision on her. If I tell the insurance company the truth about what happened are they going to demand to contact her or ask her insurance to cover damages?