She has a boyfriend but she likes to do it with her friend
Sometimes, not the majority but yes, sometimes, it is believed that having a relationship is the maximum amount of pleasure that can be achieved. Then get married and start being miserable forever. You’re not supposed to be happy, that’s a modern invention after smoking so much marijuana. However, that same naturalness leads us to see things like this. A young girl who has a boyfriend but who likes to fuck her friend more. You might think that she should have paired up with him, but it’s just for him to put his cock inside the pussy that wants it. The other things are different.