I don't think it's that strange. She's rather tall so perhaps doesn't like wearing heels that make her even taller. She's athletic, so sneakers are comfortable for her, and she's also sort of clumsy so that's another reason to wear them. In most of photos she's dressed rather conservatively or like a jock, so perhaps she felt like the white sneakers toned down the flashy top.
I just wish she would've RUN in those shoes about about 1:05am.
Another reason for sneakers: I'm 5'9" and wear a size 10 shoe, which is as big as many manufacturers and stores go. If her feet are bigger, at 5'11", she may just not be able to find cute shoes in her size.
But mostly I think it's that sneakers like that are trendy now.