Ada's Mother

The only thing that confused me in this film was the relationship between Tina and Ada's mother. Who was Tina to Ada? Early in the film, Tine tells the priest at the school that Ada is her daughter. I therefore assumed that Tina fathered Ada with the mother before she had her sex changed. But later, Tina states that she has never been with a man after her affair with her own father. I watched the film twice over two days and couldn't figure out this one point. Can anyone clue me in?