Hi I am on student visa for last six months. Me and my husband now in Australia and in my family I have just my mother in law
She is now in my country and she is also sick and she is widow.now no one who look after my mother so I want to apply visa for my mother is this is possible?

I am on 573 visa I want to change my course is this is possible?

Not possible for you to apply for her visa, she must do this herself.

For those with student visa, they can bring immediate family which means spouse and children only. Your mother can apply for visitor's visa but she is not eligible to stay long term.