Hi, If your daughter and her friends can roller skate, a skating party can be a lot of fun. There's a roller rink in Crofton on Rt 301 that does birthday parties. Another idea is a swimming party - you can have one at an indoor pool or outdoor (you would have to find one that can accomodate a party in terms of lifeguards). Or, maybe a "crafting" party at Michaels craft store; my daughter attended one where they made a "box" they decorated themselves and can be used for many different things - but they will have different crafts to choose from (My daughter uses her box to store misc. things and she loves it!) Just a few ideas...hope you find something and have fun!!
P.S. two hours for these types of parties is pretty typical and the kids love them and don't realize that it's only been two hours!