It's a figure of speech. Ok, maybe she's not exactly unhealthy. Can we get past that and agree that she's terribly thin and the last person you'd consider for this role?
Also, about the CGI, if you're gonna CGI Gal in every scene she's in, why not cast Meryl Streep and CGI Wonder Woman on top of her? I mean... It just doesnt make sense.
Besides, the picture of Gal they showed us shows her pretty skinny. I doubt she's going to look bigger in the movie. I'm guessing they're fine with how she looks.