A relationship held together only by the emotional bond of out-of-wedlock intercourse and proximity which the couple often mistakes for love.
He is clearly getting abused, but he has already gone so far with this cohabitant fornicationship that if he stops now, it will have all been for nothing.
She makes him feel guilt over the cohabitant fornicationship, repeating that she has given all of her to him over and over and what a horrible predator would he be if he still refuses to say the words, "I love you."
She wants to prove her brother wrong, that what she is going through is love and not a cohabitant fornicationship, but it will be decades before he is persuaded.