I am not familiar with Indian customs, and I'm not sure what is appropriate for a female to wear. Should a female dress more conservatively when visiting India?
It's all upon you what to wear, as India is an traditional country you can wear any of them which suits you.
It depends on where you go. If it's a large city you will see young people dress in western clothing. I think they prefer you cover your shoulders and legs but they also know you are a tourist, so I'm sure they won't hold anything against you.
If you don't look like a local- and I'm taking it you won't, they'll assume you're a tourist and forgive you for not being modest, if you don't cover shoulders or legs. I doubt it would be a big deal.
It depends upon you, what you want to wear there is no such type of restrictions in India for clothes.
On what sort of occasions would a western girl fit in wearing a Sari? Is it mainly at temples, funerals, religious and ceremonial gatherings? Under which circumstances is it more advisable to cover up? What should she she wear when meeting the Prime Minister or President, for example? Are rural villages more conservative in their dress sense and would the people there, privately or otherwise, make fun of those who were inappropriately dressed? What color schemes are common or popular in different cities at the moment? Do you think we would get beaten up if we wore a T-shirt with a slogan on it, for example?
