White background looks good, I think, but what strikes me most are two other things: the expression in her eyes looks --- erm --- not fully "here", if I can put it like that, so that wasn't the best of moments to shoot, so it seems (that fraction of a second, I mean, for this is what can happen to the eyes in the fraction of the second you exposed). And I feel she should have thoroughly brushed her hair before this to make it look less "strand-y" (if that is a word at all???).
And I guess I have to agree with that her head looks kind of "severed" without the shoulders in the frame...