Well, imho, I wouldn't consider her a bad actress. There are far worse actresses out there. The thing what bothers me about her acting though is that I feel like she doesn't add a lot of variety to her roles. I tend to think of her as the moaning/jaw quivering/pouty actress because that's all she seems to do in a movie imo.
I think she has figured out what she's good in and then sort of sticks with it. She's not taking a lot of risks with her roles (or at least not in the way she plays them) and I'd love to see her play more diverse characters because I'm sure she'd be able to pull it off.
TL,DR: I need her to 'wow' me again.