An actresses's looks, given enough time to prepare, are the least important things for her ability to play a role.
1. Character looks are re-invented constantly in comic books
2. The movie universe isn't the comic book universe, they are/can be different Earths (Marvel has 616 and something else I believe)
3. Most importantly, special effects professionals are incredible. They can basically do whatever they need to do. Whether this is darken her skin tone or change her entire face like in Looper or whatever, it literally doesn't matter. Life is easier if they start at a similar spot, but they get to get paid more if it's harder so as long as you are the other 99.9% it doesn't matter.
4. If she isn't very muscular now, Hollywood has literally the best trainers in the entire world and everywhere. The best nutritionists. Also, this becomes her job. It is her job to get built and cut up. So she will. And her company will make sure that she succeeds.
The thing to question here is that her main roles are all Fast & the Furious roles which were objectively awful movies that had the potential to be entertaining because of the silly plot idea and the audience acceptance. No one looked at those movies and said, "good golly these are fantastic actors."
People should stop bitching about her looks and start complaining about her ability (or lack). I think I was drunk every time I saw a F&F movie, so I can't comment.