Tell her that you've been thinking about the holiday and worry that in your excitement you may have have gotten carried away by inviting her.
Tell her you enjoy going away with her and know your DD probably wouldn't mind but that you don't have many years left of DD wanting to come and you really want some one on one time with her.
Tell her that you and her will have to go away another time and that you hope she understands. (Then don't arrange to go away with her if you don't want to)
That way you're not blaming your DD but letting her down gently.
I know people say you shouldn't lie but I also don't know many people like that in the real world. A lot of social etiquette is built on dancing around things and speaking indirectly, particularly in this country.
It might not be the most healthy but it's the social norm.
Saying "I've changed my mind and don't want you to come" without anything to soften it would come across as needlessly rude to me.
Are people really that brutally honest all the time?
"I actually don't want to talk to you. Please go and sit somewhere else. This is a bus not a mothers meeting."
"Your ineptitude knows no bounds. I can only imagine what you did to get this job in the first place. You're the reason we all want to work from home".
"No I do not like my haircut. It looks like someone has attached a sheep to my head then done a bad job at shearing it. I'm so pleased to see that the back of my head does, in fact, look just as bad as the front. Unfortunately there's nothing you can really do about it now and I'm reluctant to let you anywhere near my head again."
I mean, it's the kind of thing i might fantasise about but I'm not sure I could ever actually do. It would seem a social faux pas, but seeing these replies has me doubting myself.
I just can't imagine that you would be able to keep any semblance of a friendship with this person if you outright just told her that actually you don't want her to come after all without so much as a weasel word or platitude to soften the blow.