It's unequivocal that Urd -does- have Svartelf in her; she's related to Anthy. And I think it's been mentioned somewhere that while she (Freyja) keeps it pretty solidly under wraps, she does not generally get along with Urd.

Truly though, I don't think Freyja is being -allowed- to fully realize what Akio is. Subconsciously, perhaps she does, but I think Akio's got a pretty firm hold on her in some form or another.