Good morning Margaret,
Thanks for getting in touch, I'm really pleased to hear that you are looking forward to your trip with Just You. I think there is little to be concerned about to be honest, I have been here for 3 years and have never heard of a case where this has happened, however, if it was to, it would be no problem, you would be moved on to the next flight and would be met with the group as soon as possible.
I hope this helps,
Have a great Christmas,
Kindest,
Ben