You are so ed, lol. No matter what gift you get her, she is going to be looking for hidden meaning. Get her something like you get all your other friends that are girls, and she is going to think she isn't special at all. Give her something nice, and she is going to wonder if that means your boundaries are softening and she has a chance. I honestly have no idea what you can get her that says thanks for being my FWB that I don't want anything more with. If she was really comfortable with how things were, I guess go with the sex themed stuff, but adding on that she wants more makes the situation precarious.