I'm straight and I have been fancied by a gay man, that was really embarrasing. Everything he was doing was in order to get me in his bed, my friends told me the situation and I was like "but I don't want him, I'm not gay". I had to told him that nothing will happen, I was quite harsh with him because I had no solutions. He understood very well, he asked me if we could be friends, I said "no sorry, you will always think about it, it's nothing against you".
This is a hard situation, now Conzors, you know what does it feel to be fancied by a gay person if you are straight.
I guess your friend needs to understand before the straight one will talk to her.