Are the colours in the photo a good representation? From the markings and the shape of the abdomen I'd guess at Araneus diadematus but I've never seen one that colour. Maybe it's colour had changed to match its surroundings. Where did you find it? Anyway, I can't totally rule out quadratus - if you could get a good photo of her epigyne (on the underside of the abdomen) that should settle it because they're a bit different.
I'm still inclined to think it's diadematus. The shoulder humps are more obvious on the last photo and although the epigyne isn't in focus I think it looks more like that of A.d. That of quadratus is broader - you can see this here. http://www.eurospiders.com/Araneus_quadratus.htm