Just because it's a fantastical situation, doesn't mean it's doesn't relate to ordinary life. Yes, they're vampires and werewolves, so it's not a situation anyone would find themselves in. However, that doesn't make the relationship (or the controlling actions) any less problematic.
As I said before, most of the series is written from Bella's perpective, and this makes a great difference. We aren't getting the literal facts of the situation (however ludicrous and fantastical that situation may be), we are getting the version that Bella rationalises to herself. That could actually be a great strength in a work, but unfortunately the way it's plotted means that everything works out just perfectly and there are no consequences. The events of the book mean that, in the end, it really was 'all for her own good'. I'm not at all sure that's a good message to be sending.
It may be fiction and entertainment, but that doesn't mean that it cannot have powerful effects. It's horribly crafted fiction, but the ideas (if not the absolutely literal manifestation of them in the books--vampires, werewolves, freakish pregnancies and all) it conveys still matter. The great power of literary fiction llies in it's ability to convey ideas in a non-literal manner.