"Chantal" by Mary Anne Mohanraj (moh2@midway.uchicago.edu). No offense to the rest of you authors out there - and I may say the same thing about someone else right after I have read his or her story - but Mary Anne Mohanraj may be the best writer to post stories on this group. I would be absolutely astonished if this author has not written other stories that have gained recognition in high-quality, mainstream, non-erotic publications.
A lesbian woman is comforting a non-lesbian friend to whom she is non-reciprocally attracted and who has recently broken up with a jerk of a guy. She longs to hug and caress her friend and to make tender love to Chantal, but she knows that any attempt at closeness will drive Chantal away. A knock comes at the door; it is a phony pizza man, who threatens to kill the woman unless Chantal surrenders herself to his will. At the crucial moment the woman breaks free and demands that the man rape her instead of Chantal. The rapist at first seems ready to comply, but then he tells the two women to get it on together for him. Ironically, the woman's attempt to rescue Chantal will enable her to achieve her fondest desire - but under highly undesirable circumstances.
I've told you all but the very end of the story; but I think you'll still find immense pleasure in reading this well-crafted and highly erotic story.