I bought a red-ear slider from the reptile rescue and put her in my pond about 3 weeks ago. She spends most of her time hiding in the bottom. Every once in a while she sticks her head out of the water, but hides if anyone comes near. I am worried because shes not coming out to bask in the sun, and I've read that that is important for their health. Is there anything I can do to get her to come up more and not be scared of people?

it takes time for the new turtle to adjust to the new surroundings and environment. i took in 2 turtles last year from someone and they were shy in the beginning, now they beg for food and follow me around like my other turtle does.

They will indeed be shy and hide until they get used to things. You should provide some areas where the turtle can easily get out of the water as well as shallow areas in the water. Sometimes having other animals (turtles, fish, etc.) that aren't afraid will encourage him to be less afraid. I had my young turtle in an aquarium for months before he would come up to bask in my presence. Now, he's a total pig and not afraid of me.