Nubra Valley in India is generally safe for solo female travelers. The locals are welcoming and helpful, crime rates against tourists are relatively low, and there are quite a few guest houses and homestays that provide safe accommodation. However, cultural norms here are a bit conservative, hence it is recommended to dress modestly and respect local customs. Also, since it's a remote place, emergency services may not be as immediate, so a bit of caution is always a good idea. Overall, you can consider Nubra Valley a safe place to visit, but awareness and respect of the local culture and environment are highly advised.