Maybe Overland Summer if they are up for more of hiking experience.

Camp Hive for girls 12 and under is 2 weeks.

Camp Emerson in the Berkshires is closer to 3 horus away, but absolutely has several 2 week sessions, and also a 1 week session first week in August

I'm looking for a 1 or 2 week overnight camp, preferably within 2 hours of Warren Vermont. It seems like most of the New England camps have 4 or 8 week sessions.