My mother in law and my sister in law are both on the deed and title for my mother in laws house and property... how does she remove my sister in laws name... they live in brownsville, TX which is in Cameron county... not sure what kind of document needs to be used...

Sister in law ( if alive) will need to sign over her interest in the deed, normally a new deed ( quitclaim is commom)
Best to use a title attorney or a tittle company