Hard to say, due to lack of detail, if in the UK maybe Nuctenea umbratica, or a Larinioides species? Where was this taken (you have "Australian" tagged), was it near/over water? Any other photos, or can you lighten this one up at all?
It was in the bathroom (i tagged "australian" as I thought it looked similar to the australian house spider but I can see now that it doesn't - consensus seems to be a Walnut Orb - I just thought it looked a bit skinny for one of those but will it fill out as it grows? Am I correct in thinking it can still be a painful bite?
She may have recently deposited an egg sac, hence the lack of bulk, or simply be starving? I can't imagine she's going to catch much prey in your bathroom.
They are reported as being able to bite, I haven't as yet had the pleasure!