It’s unfortunate that trans people are usually portrayed in unfavorable situations in film, especially in the horror genre.
A Reflection of Fear, Private Parts, Unhinged, Sleepaway Camp, and even 2000’s Cherry Falls. All deal with a trans person with psychological trauma which manifests as violent and deviant behavior.
However, it is important to realize that these character’s are not deviants and psychotic because they are trans. In fact, they were already traumatized prior to their transition. In fact, they weren’t trans by choice, at least not in the traditional sense, therefore they can’t really be considered accurate representations of trans people.
Often in psychological horror the alternate self requires the transition between genders and is actually used to pacify the traumatized individual. The act of transitioning is needed to retain a sense of sanity and safety. In essence, the transition between genders is life saving, therefore making it a positive thing.
The idea of using the gender transition is not to portray trans people as psycho killers or demented deviants. Upon closer inspection, the usage of gender transition is imperative to the self preservation of each character who uses gender transition as a coping mechanism.
In fact, at the climax of each of these films, it is only when the transition is revealed, when the “mask” is pulled off, when the two selves meet, that all hell breaks loose and the character’s mental state is in absolute jeopardy.