I think he will have a hard time explaining the threat posed by the woman sitting in the car. He could have just as easily shot someone that wasn't even involved by mistake. He screwed up when he shot her. I'll be shocked if he doesn't get some time for her.
You don't have to prove up a threat to yourself in Texas. All you need to prove up is that you believed if you did not take deadly force you would not be able to recover your property.