Hello friend H R U? If u want to extend your sister visa pls try to get a job. Then she can extend his visa as much she interested to stay here.or u can extend her visa through qatar gov,U want to pay i think 500qr for 3months extention.Wat u r sister qualification.Try for tat...my email id s [email protected].....
If u hve any dought dont hesiste to ask me.... Send u r doughts thru this email

Byee take care