OK. I found this surprisingly hard, but I'm going to say Lynn Collins (Portia in the 2004 Merchant of Venice) as Isabella. This is kind of speculative, since I haven't actually seen her in anything other than Merchant, and I'm not really wedded to it. But I'd like to see more of her; she seems like she would be a good Isabella; and she is from Texas. And yes, this last point is relevant.
( rambling about my ideal film version of Measure for Measure, which is not, of course, the question actually asked )
( All the questions )
( rambling about my ideal film version of Measure for Measure, which is not, of course, the question actually asked )
( All the questions )