Accused of cheating... but I didn’t 😳

Guy A and Guy B are engaged. I (a straight female) have been friends with Guy A for a few years. We’re in college. Their relationship has previously been long-distance, but when they got engaged a few months ago Guy B moved in with Guy A. Since, Guy B confronted me about being too touchy-feely with Guy A and “talking about my boobs” (I had to wear a binder for a period production and it was too small. I told guy A so he could tell our costume director. Somehow guy B got that twisted up so I was bragging about my size or something). He said it was making him and A uncomfortable, I understood and made a point of not touching A even by accident or doing anything that could be misconstrued as flirting. About two weeks later Guy B FaceTimed me on Mutual Friend C’s phone and told me to stop trying to get A to cheat on him with me. I was like ??? and told him I absolutely, 100% was not, and I had no interest in him whatsoever. Additionally, A was gay, and I was sure he had no interest in me. He flat-out accused me of lying and told me to stay away from A. I have 2 projects with him so I can’t. I tried talking to A but he just laughed it off and thinks it’s funny. B definitely does not think it’s funny. I’m so lost on what to do...? I’ve made a point of not touching him even accidentally, no hugs or anything, and only talking to A when necessary about school. I’m so lost on what to do... as time goes by B just seems to get more and more sure that I’m hitting on A.