Girl using my bfs pic

this girl is saying shes dating my bf and posting pics of him on insta and had him in her bio. I asked her to take them down and she legitamently went off on me and she really thinks shes dating my boyfriend. She has blocked me and i dont have her full name to find out who she is. All i have is a first name. My boyfriend has no idea who she is. I dont really know what to do.