A vine.

The plant-girl didn't explain, but simply lowered Vivia once again. She came to face its base, or stem, or wherever, with her limbs still tightly bound. As she tried to deal with her rapidly changing bodily functions, a vine emerged from what would, humanly, be the plant-girl's waist, but on her was simply smooth plant-flesh.

The vine was thick and green, with a bulbous end, and by the way she was pulled face-first into it, Vivia surmised she was supposed to drink from it.

She glared up at the plant-girl. “Hell no-” she began protesting, but upon opening her mouth, she was thrust into the fleshy vine. She got her teeth closed just as it passed her lips, and resisted the the sordid breach.

She was slowly pulled away a couple inches, during which she noticed the impact had left a sticky white residue on her mouth, which seeped from the tip of the vine. “Drink that?!” she yelled. “Fuck no!”

The plant-girl attempted to swing her back and penetrate her mouth a few more times, yet she kept her mouth firmly shut. The white sap painted her face with each failed attempt, and although she resisted, she got the smallest taste of it, and realized it was actually... quite sweet.

Suddenly, as Vivia's tongue darted out to clean her lips of the sap, she was brought forward faster than before, and the vine succeeded in penetrating her mouth. The thick, excessively phallic instrument was **** inside, yet she denied it further access by blocking it with her tongue.

Fierce eyes turned up at the plant-girl, yet they were met only with that serene smile. “Drink,” it whispered. She resisted, yet the excess saliva made it hard not to swallow, and it did taste awfully good...