Hey red, good to see you around!!
From an outside perspective, I would personally classify little girls as its own category, someplace between submissive and slave.
A little girl would have very little power, and very little say. Daddy makes all the final decisions. So to me, this would be *more* than a sub.
However, a slave's only focus should be in pleasing her Master, whereas a little girl certainly does not always have that focus.
So if you feel the need for a label, that is where I would stick it... but I am also a big fan of just taking what works for you, from wherever you happen to find it, smooshing it all together and calling it great!
I hope it all works out, no matter what you decide.