Ex wants threesome but I’m in a relationship

So, my ex just dropped a bombshell. She invited me to an Airbnb for a threesome with her and another one of her ex. I'm in a happy relationship now, and things are great, but this offer is tempting. My ex is hot, and the idea of a wild night is exciting cuz she’s rlly a slut. But I love my girlfriend and don't want to risk our relationship.

My ex keeps pushing, saying it'll be "fun" and "no strings attached" and how there’s a jacuzzi for us. I'm torn. Do I take her up on this offer for an unforgettable night, or do I stay committed to my girlfriend? It's a tough call, and I'm not sure what to do. I’m also scared of seeing a guy fuck her for the first time