Heya fellasthis worked for me, its obviously not bulletproof, but if your copin the LJBF, you have nuthin to loose on the way out.
i got the "i wanna stay good friends with you, so thats outa the question" so i cut my losses and said "i was just jokin i wanted to see you for (some bullshit reason) then said i had to go.
messaged her later with "wait, i was just thinkin how dumb that was, since when is it a rule that you cant be freinds with someone you sleep with?" i knew she would write back, "in my experience it normally ruins friendships" (and she did write it back)
I replyed with "well you must not be very good then if people hate you after you sleep with em :P" with the jokin part after to make it seem like im messin around
she wrote back, "you dont think it would ruin our friendship?" i wrote back "in my experience it never has"
after a bullshit test she wrote back "do you know a guy john? or am i gonna have to meet him?" i wrote back with, "Top guy, ex of a friend of mine" she wrote back with -- get this
"stop being mean to me, or im going to have to sleep with you to prove you wrong" !!!! hahaha
if this works for anyone else let me know