On holiday near Kalamata with DH, DD19 and DD17. Going home tomorrow. DD17 has been miserable half the week as missing her BF of 4 months from the UK. He has arrived in Cephalonia today with his family, so she won't see him for another week. She has decided today it would be an excellent idea to travel to his villa from here - involves a 30 min taxi, 3 hour bus, ferry and a further 1 hour taxi. Then she would fly back with them instead of us next weekend. She would waste last day of our holiday tomorrow (we're not leaving until 18:15) and the flight we have paid for. Also would miss first few days of year 13 and two medical appointments that I will need to rearrange. She reckons she will pay for all the extra cost with her savings .I have said a flat no and am cross she has ruined the last day of our holiday arguing with me about this. She has ADHD and loses her phone/purse on a regular basis. She says I am being totally unreasonable as she will be 18 in 6 months and able to do what she wants. Now not speaking to me.
YABU - Travelling alone in Greece will be a good experience and won't impact your holiday much.
YANBU - This carries too much risk and would disrupt too many other things.