I think the most difficult part is finding a case where you don't have to constantly put on, and take off the scope in order for the Barrett to fit. What case do you guys use for transport? Or, is it mounted to the truck?
Any chance you're able to go to a range and rent various pistols? As mentioned by other members, I think it would be helpful for her to handle and shoot different sized weapons. She might feel the most comfortable shooting a full or a subcompact.