A girl kissed my boyfriend
So after school one day, this girl my boyfriend barely knows hugs him to say bye, and kisses him on the lips after she hugs. My boyfriend told me about it, said that he told her and she knows that he has a gf, claims that he pushed her off, and said wtf you know I have a girlfriend, and walks away. We've been together for 3 years now, he's never cheated on me before. I should believe him right?