@clownloach40
First off, welcome to the Forums.
I think you really need to talk to your "Friend" about that.
Also you might want to think about locking your game/PC when others are around that might do what you described if you have to step out of the room.
Account security starts with you.
Think about what if your Friend launched a game and decided to use the chat to say bad things to others and got your account banned. You would probably be here trying to get help but there would be nothing that could be done to help you because that would be your fault.
What others do on your account because you left it unsecure and or let them use it is on you, your responsibility and that is that.