OP is handling this badly with the best intentions.
She has a big birthday coming which legally grants her a lot of decision making privileges. You have a birthday to consider, though it may seem minor. It's a milestone she will remember, don't f*ck it up.
She is asking to go abroad on a trip that will more than likely be cancelled. You don't need to say it, common sense dictates it.
You do seem overbearing, whether it's because you are I don't know but it is how your daughter is reading you. On the cusp of adulthood you have got to change tactic and keep her onboard or she will become more secretive.
You have to show that you trust her, even if you don't. That will keep your relationship strong so that you can teach her. No comments about the other parents or the son flipping out unless she asks for your advice. Yes, his parents are likely dog rough but to her they're parents who are relaxed, allow her to drink (too much, doesn't need rubbing in) and recognise her as the adult she thinks she is. Your actions don't recognise her as that.
Sit her down, tell her you care and that you're sorry that it hasn't come across well. Tell her you trust her. Share your own experiences if you have any. Share your concerns too. Do not make a decision on the holiday and don't say no. Tell her you'd like to meet her bf. when you do treat them as young adults. If she's smart then the red flags are there for her too and she will reach her own decision with supportive guidance from you but only if she feels she can ask. If you talk to her about safe sex now she won't listen.
Their villa is booked, she isn't a cost in that regard. This decision can wait, Boris may be the bad cop for you. Tell her you won't make a decision yet, you'd like to get to know the bf. if it's really important to her you'll think about it properly and decide later on. The emphasis right now has to be on keeping lines of communication open with her and if you carry on as you are you're shutting those all down.