Looking is OK
It’s in your genes. Your eyes track attractive women. There’s nothing to be ashamed of. And if your girlfriend has a problem with it, then she’s delusional. Delusional.
Laugh at her delusion.
If you’re at dinner and she gives you shaming signals (a gasp, rolling eyes, the whole “omg” attitude)… pretend you didn’t notice and say “she’s pretty hot, don’t you think?” When she rolls her eyes, smirk and look her directly in the eyes and treat her like the child she’s being. You’re framing the relationship. You’re setting the standards and expectations. You’re telling her that you’re going to be a guy in this relationship. And if she doesn’t take the hint… then you’ll be glad you walked away as early as you did.