Finder won't open files

Hello, my girlfriend just bought a 13" macbook air over the weekend, been some minor problems that I could fix for her. This one I cannot.

She tells me this "I am having troubles opening folders, every time I got to open it, it opens for a split second and then closes the window. I can't access anything inside the folders"

I don't know what the problem is, she has restarted the macbook air and has shut it down and it is still doing this. She couldn't find the 'relaunch' finder option on her dock as well.

Please help, thanks