you have to keep in mind her height and weight. It matters greatly when you buy a board.
Also, consider binding type. You have your strap-ins and step-ins, generally.
Step-ins are convenient and quick, but they're not as secure as strap-ins, which are the more preferred choice. Strap-ins require most people to sit down and strap their boots into the board, whereas most people can just step into the step-in bindings, hence the name.
In terms of brand, they're all mostly good, really. If she's a beginner, I'd say to stick with Burton or Salomon.
You most definitely should go into a store and talk to people