Don't think of it as "groveling." Think of it as you patronizing her. Maybe you can fool her into thinking that you actually feel the contrition she thinks you should be experiencing. That would be you condescending to the child that she is. People like her have a hard time distinguishing between a person genuinely accepting her interpretation of things and somebody just blowing smoke up her skirt. Do the latter as effectively as you can while your father is alive. She deserves to be manipulated. Then, when it's just you and her that are left, you can lay some truth on her.