Hello my name is ***** ***** I will help you.
Were you going to give a free holiday to your friend or were they going to pay for it?
It is bad news I am afraid - the ex is entitled to the money back. Your friend is benefiting from the holiday. Unless your ex agreed that you could use it then you are liable to return his share.
I am sorry if this is not the answer you want and certainly not the one I want to give you, but I have a duty to be honest,
Can I clarify anything for you about this today please?
If I could ask you to rate my answer before you go today, otherwise the site does not pay me for the time spent with you today. Thank you in advance and good luck!