Girl problems

Basically this girl that I’ve been with for a while now is saying I cheated on her as I had a girl on my bf list on sc. no proof, no evidence, no nothing. Just her picturing something in her head. I explained it’s a friend that I gave advice to (idk y but I feel like I’m everyone’s therapist). She thinks I was chatting to her in the other way when I genuinely wasn’t. Dk what to do. Coz she has major trust issues and I’ve been loyal to her all this time. What do I do?