Slick you seem like a cool guy and your just trying to get some answers but im going to give you some solid advice here,... it might not be what you want to hear but from experience i can tell you, these things happen..
Shes going to South Beach, OK thats fine but if your girlfriend is attractive then shes definitly going to get hit on by guys. How will she react if a good looking dude approaches her, we dont know, you dont know because girls have a tendency to act and feel different when their B/F is not around.
No one on this forum knows your girlfriend, Only you do. However, shes a girl and we all deal with girls and pretty much all of them act the same at one point of another. She probably wants to go and just have a good time in florida BUT things happen and the bad part about it all is that if anything ever did happen. you would never know and i believe thats what kills you inside.
Even if she did decide to confess something to you, it for sure wont be the whole story because she a) does not want you to break up with her b) she doesnt want to seem slutty c) she just doesnt want you to know anything.
The really F**ked up part though is lets say she ended up going to a club/bar/lounge.... and she danced with a couple of guys, she will NOT, i repeat, will NOT tell you that a guy was grinding his D*ck on her ass because she feels "it was just dancing" and its "nothing" to bring up. meanwhile she will tell you that she just hung out with her friend and thats all.
Overall, You have to make the decision based on her actions while shes there and when she gets back, if you want to break up with her
. After your previous posts though, i believe she doesnt fully care about your feeling based on the story about that guy she was going to go see 2hours away.
My honest opinion, buckle up because chances are if shes tries to pull one on you again, You may have to cut the cord and rebound and find yourself a much better girl for you.