Its so simple. You can make visa for your sister, in two ways. Visit visa or Tourist visa. Visit visa is for 1 month, and can be extend for more 5 months with the medical report. and Tourist visa for 14 days and can be extend more 14 days without paper work. And then if you want, you can do othere two tourist visa for your sister, without her exit from Qatar.
Now its up to you, which one you prefer. If you think, that she can get easily job here then Tourist visa is OK. Its no need any sponsor signature. But if you want that she live here and get the job with relaxation, then visit visa is the best.
Just tell to your husband, to do visit visa under his name. Because in the form, his sponsor's sign is required. And it cost Qr, 220 riyal for one month. If she get job in this one month then she can easily transfer her sponsorship from your hasband to the company, who are ready to give her job And if she doesn;t get any job in this one month, then extend the same visa for more 5 months with 220/month. Just she have to go through medical commission. Which is so easy and it cost only Qr. 100....

Best of luck.........
If you need more information, you can contact me throgh [email protected] without hesiataion......