Considering her age and species the behaviour you describe is quite possibly related to egg-laying. Mature female veileds will produce eggs without being mated. She may be wandering in order to look for a suitable site to bury her eggs. Provide a bucket or similar container at the base of her basking area that will hold several inches of a moist soil/sand mixture. I would suggest leaving it there permanently if possible. Females can produce 2 or 3 clutches a year and the lack of a suitable nesting site is thought to contribute to egg-binding. You may want to increase her calcium supplementation for a couple weeks leading up to and following the egg production.