Hi Rinsha
I have heard a lot about pondicherry . It's safe for women & solo travellers. It is a beautiful place. You can also visit Hampi. It's solo backpacker's Paradise. Many tourist come from other countries here. Choose accordingly :)
Southern India is very beautiful and a little underrated but it’s also safe and convenient to travel for Females.
Also the Rajasthan side is good and safe to travel. Best of luck, Happy Travelling :)
I would suggest that Diu is a great place to travel for a solo traveller. It has beautiful beaches, forts, caves, temples and for those who are interested, booze. The union territory is very well maintained, safe and not crowded at all. Hotels and restaurants are good and affordable. It is well connected with road, rail and air. Law and order situation is very good, so suitable for female solo travellers too. It has so many beautiful place which are yet to be explored fully and appreciated. One will instantly feel connected to nature and self once you get here. On top of everything people here are very friendly and supportive unlike other popular tourist spots where race of capitalism has made people hawkish.
Sikkim is the most peaceful, eco-friendly and tourist-friendly state. you can check out my profile for more insights on sikkim. feel free to contact me for safe/hassle free travel experience in sikkim. cheers to a good life!!