The evil Joyce Miller
Joyce Miller (Catherine Dyer) is the villainess of the 2017 Lifetime film Psycho In-Law. She was the mother of Lorna Miller and the wife of attorney Dwayne Miller. Joyce was shown to be very controlling of Lorna's life, specifically in how she raised her daughter Harper. One night, while the two were out driving, Joyce got into an argument with Lorna over Harper eating her school's cafeteria food. It was during that argument that Joyce got into a car accident, during which Lorna was killed.
After her daughter's death, Joyce became closer to both Harper and Lorna's husband, Brock Nichols, enjoying the amount of control she got over them. Years later, when Joyce learned that Brock intended to marry his girlfriend (and main protagonist) Tina Williams, she became furious and began working to destroy their relationship.
Joyce began her plot by stealing the necklace Tina gave to Harper and subtly goading Tina into getting rid of Lorna's old hairbrush, which upset Harper. She also orchestrated several other acts to turn Harper against Tina and had Dwayne run a background check on Tina. Joyce attempted to use photos she found of Tina in college to convince Brock to reconsider marrying Tina so soon, but Brock remained adamant that he wanted to marry her. Undeterred, Joyce hired private investigator Grant to frame Tina for credit card fraud. When that failed to break Brock's devotion, Joyce contacted Tina's ex, Chad Davis, and set him up to meet Tina at her work, causing friction between her and Brock (who Joyce sent to the office as part of her scheme). Joyce became further unhinged when Harper began bonding with Tina's mother, who came into town for the wedding.
When Dwayne found out about his villainous wife's schemes, he confronted her as she began to run a bath. Joyce brashly admitted to trying to ruin Brock and Tina's relationship, accusing the latter of trying to take Harper away from her and coldly threatening to frame her husband as her conspirator if he went to the police. When Dwayne began to have a heart attack, the evil Joyce poured his medication into the tub and waited until he died before calling 911. Joyce additionally hacked into Brock's Facebook account to repost on Lorna's memorial page to create more tension between him and Tina.
Tina's sister, Ellen (who, like Tina, had been growing suspicious of Joyce) discovered her involvement in framing Tina for the fraud and invited her to her apartment to confront her before the wedding, threatening to expose her actions if she didn't leave Tina alone. Cornered, Joyce broke down about her depression regarding her daughter's death before shoving Ellen off her balcony (though she ultimately survived). In the film's climax, Joyce poisoned a glass of wine with rat poison she took from Ellen's apartment and had it taken to Tina, but she was stopped from drinking it by her mother. When she learned her attempt on Tina's life had failed, Joyce hid a knife in her handbag and went upstairs to attack Tina in a final attempt to kill her. As the two fought, Tina realized that Joyce was behind Ellen's absence and lambasted her for her controlling nature. Just as Joyce began to choke Tina, her mother burst into the room and knocked Joyce out. Thus, Joyce's scheme of breaking Tina and Brock's relationship failed for good when they get married, while Joyce ended up being arrested offscreen and placed in a mental hospital, where the film's ending showed her talking about her daughter as if she were alive to a nurse, having completely broken down into madness and despair after failing in her plot.