What is the ruling on a girl staying in her grandfather's house to complete her university studies and refusing to move with her parents to another village where her university major is not available, nor are there job opportunities? And is this considered disobedience to parents?

There is no harm for you in staying in Medina to continue your studies, provided you are dutiful and kind to your parents. Moving to live with them is more preferable if it does not cause you any harm. An adult of sound mind has the choice to reside with whichever of his parents he wishes, but it is recommended that he not separate himself from both of them, nor cut off his dutifulness to them. Being dutiful to parents is obligatory and is a cause for Allah's pleasure and entry into Paradise. It was narrated from the Prophet, peace and blessings be upon him: "The parent is the middle gate of Paradise; so if you wish, abandon this gate, or preserve it."