She is called the “Xidan Girl” or “Guitar MM (MM stands for MeiMei, little sister).”

Her parents are all disabled and her family is quite poor.
To collect for her parents, she started out as something of a music prodigy in a small town in Sichuan playing the Chinese lute and singing. At 17, the Xidan Girl outgrows her little town and heads for the big city, Beijing. There she supports herself by playing in the bars and subway of Xidan District. A typical scene is of of her sitting on a small blue stool playing the guitar.
This touching song is titled "maternal grandmother"
You can see the video at:
http://www.xidangirl.com.cn/03/waipo/