was i wrong to do what i did?

I have a situationship. we’re supposed to be low-key. I went to this party with a couple girls I met that same night and he happened to be there. One of the girls says her goal of the night is to have a one night stand, and she spots my bf-who’s-not-my-bf and claims him as her “target”. she doesn’t have any clue that we have a years history together, just that we know each other cus we grew up in the same area. I don’t say anything cus he and I aren’t together, he can do what he wants. he ends up rejecting her, she goes home later, but her friends stay. He asks me to stay over for the night and I do. her friends see I stayed w him and tell her. why do I feel bad?? should I not feel bad idkk. I understand how she would feel but ahhh idk.