Well, often one of the hallmarks of an unhealthy relationship is that you don't know you're in one and may even be happy with things most of the time (as long as you haven't "misbehaved" "made him angry" "pushed too hard", whatever). And I don't think not being actively portrayed as an unhealthy relationship makes this a less realistic representation of one. The hearts and flowers ending (if I recall correctly, he literally fills a room with hearts and flowers at some point in the last book?) is maybe unrealistic, but not any more so than thousands of other romance novels.