Any reasonable priced hostel/hotel near Danxia landform? Is it safe for a single girl to hike alone?

Generally, it will be safe, but you are still advised to go there with one or more companions.

Yes, there aare clear signs for independent hiking, but I remember they are mostly marked in Chinese. Thus for the sake of safety, you'd better not hike alone.

As for accommodation, there is a Courtyard of Family Qiao (Qiao Jia Da Yuan) for your convenience, which is right at the entrance of the landform. It charges not high and the hosts are very friendly.