Aspen is fine unless you have humidity issues in which case coco husk or reptibark will hold humidity in the tank better. You might want to think about blackening out the back and sides of the tank. This will help make your little no legged friend feel more secure.

The proper size prey for her really is going to be determined by her weight, you want her eating about 15% of her body weight. She seems small if in fact she is about a year old. I would question that.

Pretty snake, is she a pewter or Mojave? Seems more than a normal.