I would agree with Lily27's description.
To me, the dynamics of both types of relationships complement each other. I think you could make it as "kind and gentle" or as completely controlling as works for you.
As far as definitions go, I would say "little girl" is it's own category whether or not you have any interest in BDSM. But, I think it is entirely possible to be both little girl and submissive, little girl and slave, or any middle ground you like. I would assume that every relationship's own dynamic would dictate where you fall in definition...
Personally, I see it as somewhere in between submissive and slave (loosely defined)... but that's just me...

~vixey