Consider asking why she cut it before asking about what any guys thought. Some women are senstive about that. And the why is more interesting and can provide insight into the thinking of long-haired women.

Thigh-length to shoulder-length is drastic, so even if she wanted to do it for some particular reason (less maintenance, perceived more mature/sophisticated look, newlywed chop, whatever), she may be in shock and appreciate having someone to talk to.

I firmly believe that long-hair fans should be as supportive of possible of women who make drastic cuts. It can be sad, but cutting is as much a part of the long-hair cycle as growing it out. If women are afraid of the negative reactions they might get for cutting their hair, they might never grow it out in the first place.

Please post if you hear anything more from her.