Hi,
Years ago I went for 6 weeks to India, my friend for over a year.
I think your sister don't need a special survival kit. It makes more sence to know how "India works". Puritabs or anything similar are not necessary, if you drink only bottled water. Brush your teeth with bottled water too. Don't eat ice creme, don't eat uncooked vegetables and unpelled fruits. Think about: Peel it, cook it or forget it!
If she drinks fruit juice (you find everywhere fresh pressed juice- great!) then take it without ice (it is stored on the side of the road or walkway).
She should take syringes and needles, not every doctor has sufficient or clean ones. Take some kind of medicine with you and give the away as a nice present for new indish friends (they will love it).
Information is the best survival-tip! (Robert Pelton Young).
I wish her much fun and take care,
Dieter
Stuttgart/Germany