Until she meets Geoffrey, gentle and generous to a fault, with his two little children and an ex-wife who can only think of Tilly in terms of stereotypes.
Tilly is good enough to help look after the children for months on end while their mother is in America to treat her cancer, yet when it comes to choosing a school for Harry she can be safely left out while granny, who is barely part of their lives, is invited to help choose the school.
Though it is fine for Tilly to spend hours in the middle of the night at Harry's bedside listening to his nightmares and the gruesome stories he hears at school, her suggestion to Geoffrey that he see a counselor is rubbished as Geoffrey thinks 'I know my own child', and Geoffrey even fails to mention the letter from school describing Harry's destructive behaviour.
Time and again Tilly is driven to dislike, and even hate Geoffrey over his dishonesty, Geoffrey's refusal to listen to her hints about his children ('Minna's persistent truancy, Harry's strange, quiet slidings on and off the rails'), or to live in the real world, his refusal to tell her about major financial decisions (selling his late fathers cottage, getting a second mortgage, giving his ex-wife significant financial help for various cancer treatments that even he believes cannot work).
When Tilly finds that Geoffrey's desire to be nice resulted in his agreeing to his son's wedding at a time when it was impossible for Tilly to come, merely to save the mother of the bride the loss of the deposit on her holiday, and that he then lied to Tilly about it, pretending that they were never consulted about the date, she is finally given the impetus to leave, and to exact revenge.