These memories are from the mind of a terrified child self, but I will try to keep it to details I firmly remember.

Person A (male, I believe) and person B (female, I believe) are having a conversation indoors. Person A turns away and goes to the wall to do something, I think he might have been unlocking a door. The camera shows a perspective looking over his shoulder from ahead, focused on person B, as she falls to the floor. Person A turns around and rushes to her aid, and an angled headshot is shown of person B convulsing on the floor. After a few moments of this I fled the room with only moderate trauma.

What I know for sure: She turns very pale and appears to be choking on something or otherwise unable to breathe.

What I remember but cannot be certain of: Her eyes are not focused on person A, but up at the ceiling, and her neck appears to elongate or swell.

What I remember but suspect to be embellishments of my own mind: Her eyes turn red (in the evil way, not the drugs/fatigue way), her skin becomes all bumpy, and (this one I doubt the most) her neck develops layered feathery frills.

I have wondered whether it was an episode of the X Files, but I havent seen it in its entirety, and the only proper "alien transformation" scene from it that I can find online is quite nonviolent.

Any leads at all would help, thanks.