Masterful work as usual, RB9. Props to both of you for making such an awesome story.
I thought of a plant-girl/nymph scenario that doesn't require any props;
1.) Girl in the forest is ambushed by a nymph, they struggle until the the nymph pins her down(to a tree, to the ground, whatever) and lands a kiss. The girl spaces out, and the nymph runs away because she hears someone else coming.
2.) A second girl discovers the girl who was ambushed, and attempts to help her up; not noticing that she is slowly turning into a nymph. At some point, the half-transformed girl jumps her and tries to kiss her as well.
3.) The girl manages to break free and run away, only to get cornered by the nymph that was watching her new sister's handiwork. The two of them team up and kiss her at the same time(maybe on each cheek, maybe elsewhere), causing her to succumb right on the spot.
After that maybe a group shot of the turned three together, or them preying on another girl, etc.
I know that it's a pretty generic premise, but it shouldn't require anything except hair/skin/eye/etc changes.