YABU. My father tried to forbid me doing stuff like this at that age and kept saying as he supported me financially, he had the final say. Let's just say that one day, when I'd had enough, I packed my bags, moved out of home, got a job to support myself, sorted out the new school I was going to and never looked back. I was 17.
If she doesn't have the money to undertake the trip of her own accord, then fine - it's your decision what your own money pays towards. If, on the other hand, she does have the money, then there's little you can do (legally) to stop her from going.
All you can do is try to convince her otherwise or threaten sanctions if she doesn't do as she is told. TBH, I don't see what sanctions you could use other than that she won't be allowed back into your home if she goes against what you have decided. Just be careful if you take that stance - she just may take you up on it and never come back. That's what I would have done.
To those that say she is a minor, someone's already mentioned it but I'll slip in a little reminder - once you are over the age of 16, you can do anything you want (even in this country) the same as an 18 year old except:
- Smoke (minimum age of 18)
- Drink in public areas (minimum age of 18)
- Buy alcohol (minimum age of 18)
- Drive (minimum age of 17)
- Get married without your parents' permission (minimum age of 18) [but you can get married with their permission from the age of 16]
- Vote (minimum age of 18)
- Buy knives (minimum age of 18)
If your daughter took herself off to Magaluf without your permission and you went to the police, they would laugh in your face tell you there was little they could do unless you could prove that she was taken there against her will.
Long story short, choose your battles carefully. I think the best way to approach this is to
- Explain to her that you are worried about her taking such a holiday and would prefer for her no to go
- Explain that if she does decide to go, there is little you can do to stop her but you will not pay anything towards the cost of the holiday and she should meet this herself to show that she can be responsible
- Explain to her the risks involved in going on such a holiday and how she can stay safe and protect herself
- Insist that if she does get the money together and decides to go, she must agree to contact you at a specific time each day so that you know she is safe and well.
Treat her like a reasonable adult and hope that she will respond likewise. Teenagers don't react well to ultimatums but most will respect you if you respect them (regardless of how the media likes to portray all of them as feral weasels).