Ouch, i can see why that experience your friend had with the teacher would induce those strong feelings. It's obvious you don't grudge your friend that comfort so the jealousy is more about an unmet need in you. Can you see those feeling you're having as information? That's all, it's just data that is telling you that you have a gap in your life, that you are needing emotional and physical intimacy. Perhaps you're grieving for what you've missed out on growing up.

Also your friend was in need of that experience and your teacher recognised that and met her need. That's a good sign because now you know she is open to meeting others needs where appropriate. And maybe some day she'll meet that need for you.