Frosh are mostly housed with 1 or more room mates depending on residential life's evaluation and if the student herself specified certain living conditions. Rooms are typically very comfortable and huge. After freshman year, most upperclasswomen are able to live in single rooms. Each dorm has their own unique personality. If you're looking for peace and quiet, Rhoads or Haffner would be a great fit. If you like spending time with new customs people and are into the whole community environment, then either Pems/Rockefeller/Radnor/Denbigh would be a great fit. There's free laundry for everyone!
A student's social life is whatever she makes of it. If you're looking to meet new people then you would have to take the initiative to join groups on campus or in the bico/trico. If you're looking for a more party kind of atmosphere, there are parties every weekend in the trico and bico and upenn. There are campus groups that may interest you that meet on a weekly basis. There is always something to do on campus.