Girlfriend is friends with someone in court for sexual offenses

My girlfriend is friends with someone facing a serious sexual offence case. She says she knows him well enough to be on his side. I've always gotten a bad feeling from him and I'm struggling with how comfortable I am with her support of him. Am I being unreasonable and how would you navigate this disagreement in a relationship? She has refused to give me any information regarding it and i'm struggling to understand why she is so quick to be on his side? They have been in the same team for over a year at work. They have also recently started talking outside of work which is daily. The job is remote, they don't live close to each other so haven't met up.