Well, a followup could fix that. For example, if the next video were something like...
One week after Anne's encounter with the horse, she's still not able to get back to normal. She's in her room, lying in bed on her back with her legs spread, trying to get off with a large dildo, but it's just not enough.
Meanwhile her son is outside her door, watching. He looks down at an injector he has in hand(presumably with contents partially extracted from the horse) and injects himself. His cock and balls grow gigantic and horse-like.
Anne has turned over onto her knees and is trying from THIS position, hoping the dildo will accomplish more. It's isn't, but as she pumps it in and out, her son approaches and climbs onto the bed behind her. She pulls the dildo out for the next shove, and he replaces the dildo with his cock and forces it halfway in. She gasps, and looks back, seeing who it is, but before she can say much more than his name, he shoves all the way in and fills her up exactly how she's been longing to be filled.
He fucks her, with her biting her pillow partway through. Her belly swells a little with cum, but he grabs one of her legs, loops it over his shoulders, and fucks her on her side - forcing her face away from her pillow so he can hear her scream. He cums, filling her belly a bit more as she cums wildly.
Cut to him sitting up against the head of her bed, as she titfuck/sucks him lovingly. He fills her already partially bloated belly with cum, bloating her completely. Fade out with her staring up at him, dick still in her mouth, groaning contentedly.
...then that would justify his presence in this video.
