Honestly I think Ibelina being perfectly aware of his feelings but she has always seen him as a son, not as a lover. Her main reasons for wanting to be near him has been mostly to make him feel the warmth of SOMEONE who loves him dearly since he never had that from his parents much less his servants, and him falling in love with the heroine was just too heartbreaking so she wants him to at least feel love and happiness before that. On top of that, the difference in social standings mean they literally can not be together, she would actually end up as an unidentified corpse in a river if their relationship got more intimate. At least the heroine is a princess.