Hii aspirant..

There is no issue if your sister wants to to pursue post graduation diploma course in dietetics and Food Technology if you are successfully passed Har undergraduation in B.Sc. (Pass/Hons) Home Science or BSc (Hons) Food Technology, BSc Microbiology, BSc Biochemistry, BSc Nursing, MBBS.

If she have done her MSc from home science food and nutrition there is no issue as the eligibility is just that the candidate need to have successfully passed the BSc(pass or Honours) course in any of the above mentioned departmen with aggregate percent of 55 or more.

Hope it helps. 

Best of luck.