New and need advice

Hello, so my problem is my SO (sub) has trouble getting 100% into it sometimes and also she can get stubborn. For example I'll ask if she's going to cum again for me and she'll just say no... And idk how to deal with it. It's hard to stay dominate when I can tell she's not fully into the moment. So I guess my question is what can I do to punish her? I think better foreplay would help any suggestions? What can I say in moments like this***? And also if you have any other general thoughts I'd appreciate it. She likes choking and spanking.

***I especially struggle with knowing what to say