I'm aware of the similarities, but so far, it has not been confirmed if the devs used those plans or if they just looked at several model ships or their plans and came up with their own design. If they had build the brig to truly resemble the Fair American, they would have surely named her as such. Somaybe she was loosely inspired on by the Fair American, but we simply don't know. Keep in mind that there were a lot of brigs sailing these days; it was quite a popular rig. So she could just as easily represent some other brig.
The Fair American is a nice model though.
~Brigand