Homicidal

A mysterious woman named Emily (Arless) convinces the bellboy (Richard Rust) at a local hotel in Ventura, California to meet her later that day at a local justice of the peace to get married, offering him a thousand dollars in compensation. Baffled by the request, he agrees. The two arrive at the justice of the peace's home late in the night, and pay him to marry them. Emily then savagely murders the justice of the peace during the ceremony, and flees. She later gloats to a mute, invalid elderly woman named Helga (for whom Emily is a nurse and works for a wealthy family) of her deed.
The police investigate the crime and learn that the nurse was given the name of a local flower shop owner Miriam Webster (Breslin), who has an alibi of the night of the murder. It is revealed that Miriam and her brother Warren, who has recently returned from Denmark after the death of his last surviving parent, are heirs to Warren's father's estate. The two talk about how Warren's father was abusive to Warren growing up and the details of the will. Miriam stands to inherit the estate if Warren dies before marrying, as Warren's father was a misogynist who went out of his way to make Warren his sole heir so that only a male child of his could inherit. Miram also confesses to Warren good news of her own, that she is engaged to be married to her boyfriend.
That evening, Emily breaks into Miriam's flower shop and wrecks the store. She is interrupted by Miriam's boyfriend, who comes to the store because he did not know that Miriam had left early that evening. Miriam and her boyfriend arrive at Warren's house the next day to visit Helga and confront Emily. Helga frantically tries to communicate with Miriam, who later finds out from Warren that Emily is actually his wife; he had hired her to take care of Helga and ultimately married her. Miriam later overhears Warren and Emily talking in the next room but does not see them together.
Miriam's boyfriend learns of the murdered justice of the peace and that Emily resembles the suspect. Miriam ultimately goes to visit Warren and Emily, having realized that Emily is a murderer. She enters the house, and sees Helga descending the staircase on the stairlift. As she nears the bottom of the stairs, Miriam witnesses Helga's severed head fall off her body. She is then attacked by Emily; the two fight, and Emily removes her wig and prosthetic teeth, revealing herself to be Warren.
Afterward, the police talk to Miriam as the truth about Warren is revealed: Warren was really a girl. The secret of the child's gender was known only to the child's mother, Helga the housekeeper, and the county clerk (who later became a justice of the peace), who had been bribed to enter the birth of a boy. This was done mainly to avoid the murderous wrath of Warren's father, who wanted a boy and would have harmed the child. "Emily" was an alternate identity Warren had created overseas to be able to live as a woman away from those who knew him. When Warren's father died and he learned of the clause in the will that would have denied him his inheritance if it was known he was a female, he resumed the alter ego of Emily in order to kill and silence those who would know the truth about him.

Question: Who is a mute, elderly woman?
Answer: Helga