Best friend who's engaged?

Isabelle • KFHS🎓2018 🏳️‍🌈 USAF✈️

Okay, so tonight I was taking my best friend home. Earlier she had asked for my phone to text her fiance. My friend and I had almost dated a while back and we are constantly (hardcore) flirting with one another. We both still have some feelings for each other, and they are strong enough to where we almost kissed tonight. She asked her fiance if he would be okay with her kissing me. Now, normally I would be okay with the idea of us kissing, and I wouldn't mind kissing her. But the thing is, I feel like I'm intruding on their relationship. Even when she got the ok from her fiance. ( I pulled away because I didn't want to interfere with their relationship.) Things aren't awkward between us, but idk if I made the "right choice." I could have gotten a kiss from my dream girl, or did exactly what I did and maybe save a relationship. What would you have done and did I make the right choice?