[If it was indeed an accident, then the notion isn't completely out of the question, but there is still Clovis and various other people Lelouch has touched with that ugly power. Forgiveness has long since departed the confines of her mind. But she doesn't want her sister to know that. Not just so that she will grant her permission, but because she knows how important their relationship is to her.]
I'm not certain. That is something I will not know unless I have seen the footage.