Take your wallet out and put a generous amount on the table to cover half the bill and tip. Don't say anything about your expectations. Then you see the reaction. If she takes it for granted that you pay, and you don't (I wouldn't), then maybe you are better off if she becomes your ex-girlfriend.
There were times when the gentleman would pay the bill and expect non-monetary compensation later. These times are over. Men and women are equal, there is no reason for you to pay for everything.
There would an exception if one of you joins the other going to some venue mostly to please the other (like if your girlfriend joins you at a football game even though she has not much interest, then you pay for both tickets), or if one of you has a lot more money than the other and picks more expensive places than the other can afford. So if your girlfriend can't afford more than McDonald's and you want to go to a Michelin star restaurant, then you pay. And if the girlfriend has more money, which isn't entirely unheard of, then she can pay.