I did on average 3-4 women at once during my MLTR experimental stage. One thing i learned was that if women suspect you are good with women and you are "gaming" them - they will ALWAYS ask if you are seeing other women... there's no time for games here; one of the few times i endorse a direct answer:
"YES I AM"
she might follow with, "are you sleeping with them?" to which you should also answer with the truth...
Any more details wanted after that should be meant with matter factly "that's none of your business". if she flips out to answers like that - then you're already you've already been too supplicant.
You have set the frame that you see and sleep with other women. And you have to do it EARLY. She has to make a decision on if to accept it or not. And 90% of the time - they will (even if they say they won't and throw fits).
Make no mistake about it though - in the back of their mind - the challenge has become betaizing you into a relationship with them. Chip... chip... chip... away at your alphaness until they can seduce/convince with their pvssy that you should be with them exclusively.
One of the best ways to combat this is to LIMIT your contact with them. 1-2 days a week max! If you're spending too much time with them - they'll have no choice biologically but to "try" to lock you down. And you will begin to entertain the thought as well.
This girl who is "ok" with being FBs - will not be ok with it the more you hang out with her.
For example: Do you really expect a girl with whom you've spent 5 out of 7 days with to be "ok" when you tell her you can't hang out with her because you have plans with another woman??? She may be able to bite her tongue and not say anything if you have a strong enough frame - but the more things like this are done - the more her pull on you will grow until one of you gives in or gives up.
This "professional" woman is already doing this. Most likely because the way you are treating her is not congruent with the way one should treat a FB. You most likely are signaling inside of her (with your actions) the same feelings she feels towards a guy who is trying to court her.
staying the night, snuggling, lovey dovey talk, holding hands, too much passion, going out to dinners, and generally acting as if you are in the early stages of a relationship are the most likely culprits whenever issues like this arise.
