My best friend kissed me in front of her boyfriend

The other day at school my best friend called her boyfriend over, and then turned and kissed me on the lips. It was really fucking weird. Then she kissed him and he turns to me and goes “ours was better”. She then kissed me in front of my boyfriend the best day. And idk, I just feel very weird about the whole thing. And then in our next class, she goes “Let’s stop kissing its weird” when she’s the one who kissed me. I am really confused at this point. Why is she kissing me when we both have boyfriends and she claims to be 100% straight?