Is Ubud District safe for solo female travelers?

It's relatively safe. You can be scammed because it's a touristic area: locals can ask abnormal amount of money for very simple service, so always ask the prices in advance before you will take anything. Also bargains are fine. Sometimes men could approach you and ask for a photo. In one situation my friend one stuck on the road because of her bike and the local guy stopped to help her. But unexpectedly he started to masturbate. Which is crazy. So she ran away. Once a grab driver started a convo with me how good is his sperm. So men here like everywhere. If you ride a bike just be careful on the road, because traffic is a bit unpredictable and roads are not easy