It almost looks like, as if Lamia has very lot fun with Dawn;-)
Could it by possible, that Lamia has only precautionally gagged Dawn, because Dawn would other ways loudly squeak of pure enjoyment?
Could it also be possible, that Lamia use some holdover of Dawn's and Sophia's "Lazy spring afternoon"?
Than is only Sophia missing, to have some fun together with Lamia and Dawn=)