Still let dd bring friend on holiday

You all her how she'd feel if it was her sister who's fallen out with a friend, and that now her friend would not be able to come. Would she think that was fair?

No, of course you can't uninvite the other child. Are you seriously considering this?

In fact, I was wondering if there was any scope to go further and allow one or the other DC to invite a friend,if any of them have one who would be available at such short notice, and if it would be appropriate for them to share a room with the two 9 year old girls (or if rooms could be juggled to make this work). Given that you have already paid for accommodation for an additional child.

Your 11 year old DD will clearly just have to suck this up. From how it sounds, she isn't blameless in the fall out?

(I only have one DD and she was horrendously ditched by a friend a few months ago - in those circumstances I would have been reluctant to put her in a position which made this feel worse - tho I still wouldn't have disappointed another child because of it, if I had one.....)

My younger daughter had a friendship issue which meant uninviting a friend while her sister still got to bring her friend. It created bad vibes in the end as it created a three is a crowd dynamic versus when only the two sisters are away on holiday, if it’s just the two of them, they do hang out together

Why on earth would DD2 pay the consequence for this?! Or her mate?!

She doesn't get to set the rules. Tell her it will be fine and discussion closed.

I think yrs 6 and 7 are quite tricky friendship years in their different ways

Obviously you don’t punish poor dd2 or her friend by uninviting the friend.

It sucks for dd1 that she no longer has a friend to bring, but that’s just life. Sometimes the timings are bad.

She can share with someone else as you’ve said and not be feel so left out.

well no, you can;t uninvite a child you have invited to go away with you , that would be really rude and unkind. And also unfair on your DD2.
I can understand he is disappointed her friend isn;t coming any more, is there any chance they will make things up before half term or is it too far gone ?
But ultimately it is what it is and she has to accept the situation. I would just big up the holday in general to her, ask what she's looking forward to, let her choose an activity, generally distract away from the lack of a friend and focus on the 'good time to be had by all regardless of who is there'.

This is the moment you teach her that she needs to deal with her relationship issues better and not punish other people because of her own fallings out!

Absolutely don’t punish innocent DD2 because her sister has fallen out with her friend!