Transitioning back to friends

I (f27) have been seeing someone (f26) for about four months. It’s mostly been distance and we hadn’t picked an official label, we were friends long before we started dating. Things have been kind of ambiguous with her overall not being sure she is into women but wanted to try it with me. She came to visit for what I hoped was a couples trip only to learn that she just wants to be friends. I feel like a jerk for being sad and ruining our time, I’m just sad and not sure if I want to finish out our trip together. We have been hanging out with my NP but had planned to spend a few days away just the two of us and I don’t know how to handle that right now. My NP is supportive but isn’t available to go on our getaway with us to make it feel less like a couples trip. I don’t want to ruin our friendship but I don’t know how to transition back instantly. Any advice on transitioning back to friends would be helpful.
TLDR: how to go back to just being friends quick?