It all depends on what you mean by a speaking in a natural unforced manner. I was taught English from Ladybird books by my Swedish mother, starting from the age of 6, and gradually moving on to more sophisticated literature, then to real people. I would certainly say I am fluent and most people don't spot the accent, it really is very slight. I dream in English, I write poetry in English, I conduct the whole of my working day in English, I speak to my children in both languages without feeling hampered in either. But I was 29 before I actually moved to England. It had come to feel like my native language long before then because so much of my reading and thinking was in English and I took every opportunity to hear the language.
My brother who started learning German at the same age is now very fluent in German.
Now we were probably unusually driven and not every child is going to be the same. But I wouldn't rule out the possibility of a relatively high level of competency. Agree with Moondog, though, that one German day a week doesn't seem like enough. You need daily or almost daily reinforcement.
I haven't got much experience of starting to speak a new language, as we never really spoke English at home. One good thing my parents did though was to get in a young English au pair over the summer just to tutor us. We are still in touch, she's a lovely lady, and it did a lot for our English.
With my own children, I have spoken both languages from the start, so they've never known any different. But I am going to start teaching dd more French now- school seems to be progressing too slowly- so we'll see how that goes.
I can think of a few things I would probably do in your case:
Have a special fun activity that is only for you and your dd and that gradually introduces more German. Something little babies can't do, something that is just her own.
Once her reading in English is established, introduce her to reading German (shouldn't be too difficult).
DVDs are good and easy to get hold of these days, but they reinforce, they don't actually give you that much active competence.
Once she has some German, try your hardest to get her into contact with German speakers her own age, whether in RL or over the internet. Nothing will get you into a language as quickly as being desperate to communicate with a native speaker.