I don’t know enough about the situation with your first therapist to comment on her decision to transfer you. It sounds like she understood her own limitations and thought you would do better with someone new.
Actually, what you are reporting is a “normal” experience some people have in therapy. What you are describing is an example of “transference”. At 17, it is normal for you to be struggling with developing your sexual identity. Whether or not you were sexually abused, you are living in a culture that can make that frightening. Therapy can be a safe place to explore your feelings about sex and relationships. It is not at all uncommon for clients to do that by processing intense feelings for their therapist.
Do talk to your therapist. Share your letter and this response as a way to start. If your therapy doesn’t feel safe, first talk about it. Yes. Talk about it. If the therapist can help you feel safe, it is often in such moments of awkwardness, even fear, that the most growth can happen.
Do remember that not every therapist is a “fit” for every client. If it still doesn’t feel right, consider whether you need to look for a therapist who you can work with.
I wish you well.