Treating My 18yo Girlfriend Like A Slave In Threesome

My hot young petite 18 years old girlfriend is a real slut so I treat her like that all the time. This time I really wanted to humiliate her so I brought her best friend to be her mistress while I fuck her. She whipped her skinny ass and treated her like a dog with lather-belt around her neck while I was eating her pussy and fucking her in doggy style until I gave her hot cum shot on her tiny ass.