Why does Eva take Liz and Norland to the house in Pimlico in the novel, One by One?

Eva, Liz, and Norland go to house in Pimlico after the drinks party for Snoop. Eva has set Liz up intending to get footage of Norland sexually assaulting Liz that she can use as blackmail. Instead, Liz pushes Norland over the balcony, resulting in his death. Instead of getting footage to blackmail Norland, she receives footage she can use to blackmail Liz.