See Cognizant mainly is a IT company. Now if your sister is studying BZC in class 10+2 then you sister can also work in Cognizant but she have to choose her career path accordingly. To work in cognizant there are some ways i.e.,  your sister have to work as a Techie or Managerial post or Legal department or Accountant etc. Now some of the career options your sister can choose is to go for BCA + MCA course. After this she can apply for walk in interview and get a job in cognizant. The second option is to study MBA (after graduation, this have more probability than BBA graduates) or she can study about corporate law etc. Thus yeah! your sister can work in Cognizant but she have to choose the career path wisely and BCA+MCA or MBA is the best options to go for.

To know more about BCA visit the link below:

https://www.careers360.com/courses/bca-bachelor-of-computer-applications

To know more about MBA visit the link below:

https://www.careers360.com/courses/mba-master-of-business-administration

I hope this answer helps. All the very best for your future endeavors!