She's your worst enemy and you find yourself locked in the library together. Take it from there babe............
This actually happened twenty years ago but I do not think it is a story which a male can write well.
I had a Hindu girlfriend aged thirty or so whom I considered to some extent frigid. Even kissing on the lips was taboo. This was caused by her repressive religious upbringing. She lived in a sheltered environment and rarely went out. I met her at work and in general we spent time together only during the day.
That summer she convinced the people she lived with that they should allow her to go on holiday with her best friend, "B". It was a threesome and I paid for "A" and myself. I had to go to the resort independently so that my presence was not discovered by the sheltering family.
Contrary to my hopes, nothing went on with me in the holiday flat. I slept on the sofa while the two girls shared the matrimonial bed.
In London after the holiday was over, "A" showed me the holiday snaps. Amongst these were several of her taken by "B" on the bed in which "A" was wearing only panties, not even a bra.
I said, "I hope "B" is not lesbian" to which I was given the surprising reply "If she is, I would have to give myself a ritual bath every day."
I replied, "So I can´t even give you a kiss on the lips, while if you had a lesbian relationship you would only have to have a ritual bath."
A writer could take the story from there.
In a later discussion with "A" I asked her if she would ever have sex with a woman and she replied, "I think I would do it with "B" if she asked me, just for the experience."
A friend telling you her sex stories when you really what to be with her
How about two girls tried to experiment their sexual orientation, got aroused and fucked each other for the whole night (or day) while they were alone?
How about...two ladies in a long-distance relationship have regular phone sex sessions...one of them surprises her gf by driving all night to her gf's city...and then calls her after she's there. They're phonesexing, she's telling her gf to do things...and do more things...and finally to draw back the curtains and stand by the window (with her gf thinking it would be kind of exhibitionist, not expecting anyone to be there)...and there she is, outside the window.