Hi GoodGuy,
I can't answer all of your questions - and a lot depends on administrative delays which cannot be very well predicted.
If your friend marries an American in India - and her husband is willing to stay 90 days in India, then they can use "Direct Consular Filing", otherwise known as DCF - to apply for her green card at the US consulate in one Indian city (I can't remember which). This process would be the quickest way for her to get to the US.
For more information, search on this forum for threads with the word DCF in the title.
After she recieves her green card and comes to the US, she can file N-400 to apply for citizenship in 3 years minus 90 days. That N-400 process can take from 3 months up to 2 years depending on the district in which she lives.
-Ocelot