Your man playing video games online with underage girls.

My man has been playing Grand Theft Auto 5 and Mortal Kombat with a 13 year old girl and it is really bothering me. He has also befriended her on Facebook. I have brought this up to him and have wittnessed them play and to me that's all it is. He has repeatedly told me over and over that he is just helping her in the game and that they are just friends but she is constantly messaging him on Facebook and tagging him in posts. It is really bothering me because I think she's crushing on my man and I do not want him getting in trouble with the police. What do you guys think about this?