Cousin In Law

I have been married for 2 years and dated my wife since we were both 18. Since about 3 years ago, my cousin in law, her cousin, has been extremely flirty. When it started she was only 15 and though I felt uncomfortable, I have always found her attractive. Now she’s 18 and a senior in high school. She has been for a few months now and the flirting was dialed up to 11 ever since. Finally this morning, she skipped school and showed up at our apartment. I have the day off but my wife is at work. As of a couple hours ago, I cheated on my wife for her. I feel guilty but I could not help it. She is unbelievably sexy and after 3 years I couldn’t hold back any more. We had sex all morning and she made it clear before she left she wanted to do this again. She’s been on birth control so there’s no pregnancy risk and it makes it even hotter. Can’t believe this situation but I’m not complaining