Sex With Gf And Her Friend

I’m 18, have been dating my girl for 2 years. She’s really pretty, huge ass and nice titties. We’ve been fucking for the past year and it’s been amazing. She was on a trip wit her best friend recently, her friend too was with someone, well, it was an ill defined relationship. They were friends except they wanted to have sex but also we’re slightly more than friends, confusing.
During the trip, the guy she was seeing said he didn’t want it anymore and just vanished. She got real sad and was saying shit like she couldn’t trust anyone again and also that nobody wanted to make love to her. It got quite frequent, the crying.
My gf told me to do something about it, I talked to the guy and he wouldn’t listen. One day she got sick of it and told me she wanted me to fuck her friend. I declined but they came over anyways. My gf isn’t a bisexual so she said she’ll leave, I asked her to stay. Her friend started off with a bj, she was new to it, eventually we started fucking, my gf got visibly horny and joined us. We fucked each other all night long, turns out my gf is bisexual.

Since then we’ve been fucking occasionally together.