I just thought I'd update you all . . . with an additional question at the end.
After all is said and done, DD#1's room really isn't all that bad. She has her bed and a dresser along one wall, a nice-sized window along the other wall, then her door (which she hung a full-length mirror on) and the hanging rack on the other wall. The hanging rack has 2 shelves above it, so lots-o-storage space (she won't be needing the outer coat closet or a common-space wardrobe.)
There's enough floor space left over so that, while really small, the room does not feel cramped.
She bought a small rolling desk-type thing with a shelf underneath for her printer which she keeps in the common area right outside of her bedroom, next to a couch. While it's in the common area, it works nicely as an end-table, but it's easy enough for her to roll it into her room for quiet study times.
Laura's room seems a bit cramped, but that's only because she has a whole lotta stuff in there. A TV/+stand with shelving, which includes a pull-out desk & chair, her bed and a dresser. Plus she has a pretty nice sized closet.
Vicky's room? Is definitely the cream of the crop. She has her bed, two dressers, and a walk-in closet (where she put a sitting table for make-up, etc.) I didn't see a desk or TV, but there's plenty of room to put one in if she chose to.
That being said, here's an UPDATE on dividing the rent:
*As far as dividing the rent, DD#1 told me that everybody pretty much agreed that a closet in the bedroom is worth about $50/month. So the smallest bedroom would get a $100 break on the monthly rent. (They are still undecided about the extra amount.) This seems a bit high to me. I think $25/month for a closet would be more on the fair side, but . . . ya know? . . . I'm staying out of it. 
They opted not to go with the above original plan and decided to go with the square footage.
As it worked out, basing the rent on an equal share per person, DD#1's rent is $30 less than the equal share. Laura's rent turned out to be the equal share, and Vicky's rent is $30 over. (Actual dollar amounts are rounded off, and DD#1 agreed to pay a few bucks more for equal balance just to keep peace in the family.)
Now that rent is due, Vicky is firmly saying that she can't afford anything but $20 over the even share. Apparently, Vicky's parents are paying for her rent and gave her a top-dollar limit. Vicky expects DD#1 and Laura to come up with an extra $5 each.
DD#1 said: Mom. It's only $10. But Vicky came home the other day with lots of new clothes. She bought a bigger dish-rack because she thought that the one I brought to the kitchen was too small, etc. Surely she can afford an extra $10/month!"
Add to the fact that DD#1 and Laura scrounged to get most (all) of the common area furniture . . . 3 couches, One chair (yes, there are two rooms to fit all this in), the TV and stand, and a couple of end tables. Vicky said that she would provide a coffee table and a kitchen set.
The coffee table hasn't appeared yet, and the kitchen set is a rickety old table with 3 folding chairs.
Granted, it's only a silly, nit-picking, ten flipping dollars, but don't you think that Vicky should cough that up?
I told DD#1 that I would pay the extra $10/month just to keep peace with her roomies.
DD#1 told me "No. Laura and I need to figure out a way to tell Vicky that we are not happy with what she just told us. Rent is due today!"
I wished her best of luck and told her not to turn this into a big war. I said "You have to live with Vicky for the next year. Is $10/month worth a happy home situation?"
She said "I guess. But it's still not right." Which I agree with, but I'm not sure how to best handle this situation.
Any thoughts?