Dead Alive

In 1957, explorer Stewart McAlden (Bill Ralston), leads his team out of Skull Island with a captured Sumatran Rat-Monkey â a hybrid creature that resulted from the rape of tree monkeys on the island by plague-carrying rats. The team is stopped by warrior natives, who demand the return of the creature. Stewart gets bitten by the Rat-Monkey during their escape to a waiting jeep. Seeing the bite mark on Stewart's right hand, his men hold him down and amputate it. A bite mark and scratches are then seen on his left arm and his head, respectively, and those parts are also removed. The captured Rat-Monkey is shipped to Wellington Zoo in New Zealand.
Lionel Cosgrove (Timothy Balme) lives with his domineering mother, Vera (Elizabeth Moody). To Vera's dismay, Lionel falls in love with a shopkeeper's daughter, Paquita MarÃ­a SÃ¡nchez (Diana PeÃ±alver). While snooping on the two during a visit to the zoo, Vera is bitten by the rat-monkey. The animal's bite turns her into a ravenous zombie. Lionel tries keeping her locked in the basement while simultaneously trying to maintain his relationship with the oblivious Paquita. Vera escapes and is hit by a tram.
As the townspeople assume she is dead, Lionel tranquilizes her to keep her still for the funeral. After she is buried, he returns to the graveyard to administer more anesthetic, but encounters a gang of hoodlums. Vera bursts from her grave, and kills the hoodlums, creating more zombies. As their numbers grow, Lionel conceals them in his house, and struggles to keep them under relative control with tranquilizer injections. Lionel's uncle Les (Ian Watkin) arrives to wrangle with Lionel over Vera's estate. Discovering the "corpses," Les blackmails his nephew into giving up his inheritance.
Lionel reluctantly administers poison to the zombies to "kill" them and buries them. However, the poison turns out to be a stimulant. Meanwhile, Les invites his friends over for a housewarming party. The zombies burst from the ground to attack the party guests. Lionel informs Paquita and Les of the zombie outbreak. Les escapes through a window while Lionel distracts the zombies from Paquita. Les goes into the basement, where he encounters Vera, who has turned into a giant zombie. She kills Les.
Lionel kills most of the zombies with a running lawnmower. He and Paquita fight dozens of zombies and animated body parts. During the conflict, an open gas pipe ignites, setting the house ablaze. Lionel manages to kill all of the zombies in the house. Vera, who has become a gargantuan monster with a grossly distorted head and huge breasts, emerges and pursues Lionel and Paquita to the rooftop. Paquita is left hanging on to the edge of the roof while Lionel confronts his mother. During the confrontation, it is revealed that Lionel witnessed Vera killing his father and his father's lover. Vera causes Lionel to fall toward her as she opens her womb, engulfing him. Vera then tries to kill Paquita by removing her hands from the roof. Lionel cuts his way out of his mother's body, causing her to fall into the burning house. Lionel and Paquita escape the building and walk away arm-in-arm as the fire department arrives.

Question: Who pursues Lionel and Paquita to the rooftop?
Answer: Vera