The smaller they are the more they run away. She'll calm down as she grows. If the male is much bigger than her I would separate them. He could eat her or part of her or just make her stressed out. Sand, especially calcisand is fairly dangerous for leos. They can eat it and it can clog their intestines and kill them. Paper towels or slate are much better and safer choices.
Leo looks to be a normal. Without knowledge of it's background its probably in the ballpark of $10-30 depending on size and how much someone else likes her. If you got her from a breeder and know her genetic background probably more like $20-50 based on the same things as above and if she's het for any unusual traits. She's very pretty!
On the package off the sand there was a leopard gecko on it so I don't think the sand is a problem.
What do you mean with reptile vet? I feed them enough, refill their water everyday and I use their vatimines once a week on mealworms.