At $4.00 a box, that would be 3750 boxes of cookies or 312.5 cases )based on 12 boxes to a case). How would you transport 312 cases of girl scout cookies? Rent a UHaul?
Yes, that's almost certainly how she did it. The GS deliver large orders to the local troops at a central locations, and they pick them up without paying. Later, they are supposed to return with the cash. It's kind of a consignment deal. She did the picking up part for several troops, but kinda ignored the whole "return with the cash" part of the process.
Man, you gotta REALLY love those Girl Scout cookies to pull off a stunt like that. Either that, or... "Hey Mabel! Did you know they're selling Girl Scout cookies on EBay now?"