Paula Casillas is the main villainess from "He's Dead, She's Dead," episode 3.02 of Castle.
She was played by Bess Armstrong.
Paula Casillas is the widow of Emilio Casillas, a businessman who was having an affair with a young blonde named Tori Johnston. It was revealed that Emilio informed Paula of the affair, which led to Paula poisoning him in a fit of rage.
After Emilio's death, their daughter, Marina, dragged Paula to see a psychic, Vivien Marchand. Paula was skeptical at first, until she realized how much Vivien knew about Emilio and his death. Looking to cover up killing her husband, Paula plotted to kill Vivien, beginning with buying a bottle of wine (as part of her alibi) and an ice pick (the murder weapon. Two hours later, Paula and Marina dined at Mason's, a restaurant that hadn't yet acquired a license to sell liquor. The villainess left to buy a bottle of wine, but in actuality, Paula went to Vivien's office to pick up the bottle she bought earlier, and also retrieved the ice pick and stabbed Vivien in her neck, killing her. After the murder, Paula returned to the restaurant and dined with Marina.
Paula confessed to both murders, much to Marina's shock, during their interrogation with Beckett and Castle. She was eventually arrested for killing her husband and Vivien.