Rightly or wrongly, I wouldn't have even considered the situation of the op worthy of a difficults night sleep at all. It wouldn't have crossed my mind to inform revenue in the slightest.
Throwing different scenarios at the issue for reason not to,, well, we could be here all night.
I would be pretty sure, most normal thinking folk, would absolutely help their daughter out in this situation, and not invite trouble where there is none.
I would 100% do the same.
I think most people would want to help, however its better to go in with a full understanding of potential pit falls. One of the main issues here is if the daughter moved a friend or partner in with her to the holiday home , what rights would they have? Better to have upfront rules