Not an easy task unless you can manage to get the followings:

1) She must get pure commitment from her current sponsor that they have no objection on her marriage to you and later she will be allowed to change her sponsorship under you.

2) You must have a good salary professional status (can be found in your Qatar ID) to obtain Labour Dept.'s approval for family status. Also you have to get NOC from your sponsor on this regard.

Best of luck buddy !!