If I am going on a cross-country trip in a country like India, it has to be a blend of the first four- I would exclude the bike as two-wheeler riders are at the mercy of four-wheeler drivers who may not always be merciful ( there’s ample data to support my misgivings, please look them up).
Flights because train tickets might not always be available, or be over crowded, specially during festive months, flights are also preferable when the distance is over six hours.
Buses, because sometimes I like the idea of being bathed in neon lights and truck music. I also prefer the bus journeys to be short because of the absence of toilets on most Indian buses.
Trains also when the landscape is going to look something like this:

As a woman traveler, I believe in selecting the safest option based on where I am traveling to and who I am traveling with- with close friends & family, anything is safe; otherwise flights may well be the safest.
I wish there comes a day when women don’t have to invest so much of their time picking the safest bets and spending more time enjoying their travel.