I have personally trvaled to all these places, solo or with a female friend and can vouch for them in terms of safety and experience.
Rajasthan --Udaipur,Pushkar,Jaipur, Jodhpur,
Uttrakhand-- Valley of flowers, Auli, Almore,Lansdowne,Corbett
Karnataka-- Hampi, Coorg, Mysore, Bangalore, Udupi
North East India is always a Go-go for everyone, especially ladies travelling alone. The places are really soothing and safe. One can find females on roads, in hotels and hone stays and even on tourist spots to help everyone.
Have a nice tour😊