Do We Need to Like the Heroine?

When I read a romance, I want to love the hero. But is it also important to like the heroine? After all, I'm walking in her shoes as I read. Shouldn't I at least admire and secretly want to be her, if for only the duration of the book?

Evidently not.

I haven't seen the most recent Twilight movie, but I've read all the books and frankly, Bella is a puzzlement to me. She behaves in a heroic way in the first book, sacrificing herself when she thinks her mother is in danger, but after that shining moment she went downhill fast. She's whiny and manipulative. She strings Jacob along shamelessly, keeping him dangling as a second fiddle in case things don't work out with Edward. She engages in dangerous behavior just to get attention. She throws a tantrum because Edward guards her purity (and his own!) before they marry.

I just can't find much to like about her and I'm having a hard time understanding why these two fine young men are so enamored of her.

I'm in awe of the success of this franchise. Stephenie Meyer is an amazing writer and any author who says she hasn't smacked her own forehead and exclaimed "Dang! I wish I'd thought of vegetarian vampires!" is only kidding herself.

But I still really don't get Bella.

Can anyone enlighten me?