She is amazing and her name is May Erlewine.
Her voice gives me goosebumps at the end of that video!
These photos are from Hoxeyville 2010.
May and Seth together on stage is magic, so much love between them is translated into their performances.
I highly recommend that you check them out some more.
They are also very active activists. Everyone has their own way and theirs is through their music and their farm.