Damn, won't let me edit. You could always tell them also that whoever sleeps on the roll-away bed or whatever it is, gets a discounted rate and the other girls pay more. It would still be less then seperate rooms, but then no one feels shafted for not getting a bed. Or they could alternate beds.
Whatever, or sleep in the same damn bed! Whats the big deal. I have slept in the same bed as lots of my friends over the years to save money on additional rooms. Granted, I was like 18-25 then, but whatever.