I might be biased since I'm from there. But kerala should be on top off your list. My town sees a lot of solo female travelers from around the world and they all seemed extremely pleased with their decision. The locals again are a really nice bunch throughout the state and you get a tranquil mix of diff vacation experiences.
Any place, yaar. Go wherever you would like to travel first. Just be careful, observe people around you. Have itinerary/ stay in place before going to anywhere. Also, carry pepper spray and you are good to go.