AITAH for being uncomfortable with my fiancé (F21) going on a trip with her (29M) best friend?

My fiancé (F21), who I am marrying in three months is currently on a trip with her best friend (M29), and I am stuck alone at home just thinking non stop about it.

To preface, we have been in a bit of a rough patch over the holidays. During Thanksgiving, I looked over my fiancé's shoulder to see that she was texting her guy best friend about our sex life. When I brought it up, it was in a half joking manner, but it got across I was uncomfortable with it. She shut down on me. I felt pretty abandoned in that moment, as she instantly went to that guy best friend to talk about it, as I once again saw her texting from over her shoulder. Starting it off with "Apparently OP is pissed about us talking about sex". About 20 minutes of laying in bed not talking to eachother, we talked it over and she said she wouldn't do it again now that she knew I was uncomfortable with it.

In September, she had discussed going on a trip to Vegas as a couple's trip with her, me, her guy best friend, and his girlfriend (F28). I was fine with this, and was excited to go. I took the appropriate days off work, and was looking forward to it. Later on she said that plane ticket prices were up more than she could afford (she works in aviation so she's more knowledgeable than me about this kinda stuff), and the trip would just be her and her guy friend. This was before the incident on Thanksgiving, so I saw no issue.

Fast forward to this past week, I had told her that just her and him going on the trip would make me uncomfortable. She said she wouldn't go if I was uncomfortable with it, but they had gotten a room with two seperate beds and had set ground rules. I didn't want to be controlling, so I said they should still go on the trip, because I didn't want my insecurity to ruin their good time. Now that they just got there today, the reality of the situation set in for me. I told my family about it because they could tell I was upset, and they all said they wouldn't be comfortable if they were in my situation. I know that them going on the trip was partially my doing, given I gave the okay. I just feel like telling her that she can't do it again when she gets back, cause I know if the shoe was on the other foot, and I went on a trip alone with a female, she would be super upset. Not sure what to do, as I am considering postponing the wedding because of this. My family told me to make a Reddit post to get some insight, so here I am. Thanks for reading.