Well, to tell for sure you need to 'look up her skirt' so to speak. ;-) We'd need a nice macro-shot of the area between her hind legs. At this age if she's male she'll have a couple rows of pores developing.
I agree with Matt though, it looks female to me. At that age I've noticed that males already start developing larger crests and noticeably wider foreheads. It's more of a gestalt than anything else, I suppose. What is she, like 14-15 grams?