Ok. I think recessive white produced bluer legs while dominant produces white.I did some digging after seeing your post and most everything I can find is from 5+ years ago, but it's indicating that most White Ameraucanas are recessive with only a few dominant white flocks in existence. I get the feeling recessive white was preferred due to being superior at covering gold pigment as compared to dominant white, just based on what I've reading just now.
To the OP, if your bird is dominant white, crossing her to Lavender would make Paint as Amer says, which is white with varying amounts of black flecks. The chicks would still carry lavender as well.
Splash crossed to Lavender would make Blue chicks, all carrying Lavender. A Lavender bird crossed to anything but another Lavender or lavender-carrying bird acts the same as a Black bird because of lavender being recessive, so this is essentially the same as crossing Splash to Black.