Simple. She doesn't. She never has, and she wants to kill him now. Anyway, it was confirmed that they are siblings and Morgana was the first to know (apart from Uther xD)
During the first few seasons, she did 爱情 him, but it was no 更多 than a sibling 爱情 which later turned to hate as fear of persecution turned Morgana against him and everyone else in Camelot
