Mr.Nitin Chopra, the invitation letter from her is not sufficent, your cousin sister should get a certificate that she is the student in the college/unversity, besides, the following required documents are also required:
1. Copies of the kinship certificates (e.g. marriage certificate, birth certificate);

2. Invitation from the applicant's relatives from China with a Copy of the relative's passport & residence visa;

3. A No-objection letter from the applicant's company;

4. 1. Original passport with blank visa pages and validity of more than 6 months;

5. UAE resident visa valid for more than 6 months. (Excluding non-GCC applicants);

6. Application Form which must be completed neatly and signed by the applicant;

7. One passport photo (and the photos of the applicant's accompanying persons included in his/her passport if they plan to travel with the applicant.);

8. Copies of the data pages of the applicant's passport and UAE resident visa.