I'll admit I too was hoping she'd have a bit more screen time than five minutes, but overall, I'm not surprised at how small her role is. Us Barbz can consider her an actress because we know of her background in drama and her passion for acting, but the GP and (to extent) the film industry don't. She's not currently seen as a serious actress and if she ever wants to be, she'll have to start small.
I've always known her role in The Other Woman would just be a small one to cut her teeth on, and even if it's smaller than I would've liked, it still serves that purpose.
