Probably the closest place to stay is in Dumfries/Quantico...
Hotels there: Days Inn, Comfort Inn, Econolodge, Hampton Inn, Holiday Inn...
she can check the Trip Advisor website for reviews and go off the hotel's website for prices (not Trip Advisor's, they always list the prices higher than what you can get them for). Does she have acess to a
AAA membership for a room discount?
I wish I could recommend a good hotel, but we used to live there, so no need to stay in a hotel...
I'm assuming her bf is stationed at Quantico? If so, maybe he can get her a military discount...
Maybe someone else has good advice too...
HTH!~