Debby, if you wanted to soften the blow a little for your daughter who's set on BWV, explain to her the benefits of OKW's proximity to DTD.
My DD has taken friends with her a couple of times. When at OKW they enjoyed being able to take the watertaxi through to DTD and wander around there. Depending on your park tix they also might be able to take themselves to DTD and spend a day/afternoon at Disney Quest. With the new slide now at OKW to boost it's pool facilities I think OKW is a much better option.
It's worth checking out the happenings at the HOB, this was a couple of years ago but (I think on fridays) they did run teen "disco" nights at the HOB ( I think the music was more contemporary than "disco" but I used that for want of a better phrase).
If you have a choice between a 2 bed at OKW and a 1 bed at BWV, IMHO there is NO CHOICE. Go with the 2 bed, everyone is going to feel a hell of a lot more comfortable in the bigger accommodations. While it's very nice of you to offer to let the kids have the proper bed, I think that two adults sharing the pull out sofa is not really a workable option for a longer holiday. For a couple of nights, at a push, it'll do the job, but if you find that you and your DH don't sleep well on it, it's going to make for a miserable holiday for everyone concerned. If you're a little tight on points, I'd still go with the 2 bed and either rent a few points to cover it or find an off site hotel for a weekend. If you're flying in on a Saturday, then getting something like a kids suite at the Holiday Inn would be a workable option, most people do little more than grab something to eat and go to sleep on their first night and it would save you 40-50 points. If you were planning a couple of days at Universal, then staying a couple of nights at one of their hotels and making use of the excellent "front of the line" perk for USF hotel guests is going to save you a hell of a lot of time queueing. If you're going at a busy (school holiday time) this perk is worth it's weight in gold. Again if you're staying at a USF hotel, you could let the older girls explore the parks on their own for a couple of hours, if you decide you want to make your way back to the pool. Depending on your schedule, say if you flew home on a Saturday/Sunday you could book into one of the USF hotels for the last 2/3 nights, again saving a lot of points.
I know how bossy and opinionated DD at 15 can be, but if you explain it nice and calmly along the lines of, you can have your friend come with us and we all stay at OKW where everyone gets their own beds/room or we go as a family of four to BWV. Whichever you want darling

. You can always blame Disney, showing her the room occupancy for a one bedroom is only 4 people

.