Are our friends being cheeky?

I think this is a very good response!
I'm a soft touch (but am generally quite good at saying no) so can see myself adding something like 'I hope DD is okay, she is such a sweetheart and it's always lovely for you to have extra time with them when they need support, but i know it can be such a worry. Here if you need me' And then... probably opening myself up to more DD invites in future....

This is good advice

They can be ask and you can refuse. Seems odd though. Why can’t 40 year old rearrange her visit to her parents.

This wouldn't bother me at all, in fact if my mother was down for a few days and I was going out with friends I would bring her along. Surely when adults spending time with each others friends is OK and there is no reason not to include her if you can accommodate her. She is not some sad old spinster she is a human being who is spending time with her parents.

Anyway the wife of couple has texted (meal is later this week) and said their DD will be with them and has asked if she can join us for the meal at ours

Even if it is worded in a tricky way, the fact that she has texted about this to ask if DD can join means that she knows it's not a given and you have this chance to say something, so don't be all polite and suck it up or you'll just end up resenting them and their DD even more. This time it's a bit harder because you've invited someone else so it's not like you can say you just wanted to see her and her partner, but you're going to have to say something or DD will keep coming. I think respond simply and clearly ignoring any subtext that you have no choice, because you do, so use it: "Thanks for the heads up. We'd rather just see you and xx so if you need to rearrange for a time when DD isn't staying, let me know. Nothing against DD, it was great to catch up with her last time."

I would just say no and stop seeing them so much, there is too much going on with their daughter .

Just say no. Poor dd at 40 tagging along. So sad.

This is so strange to me. Why not? I mean I get when you’re like 13-21 not wanting to but surely you’re able to take something from someone regardless of them “being your parents’ age” now you’re a fully fledged adult? (I’m asking out of genuine interest not trying to goad)

Clearly op and several people here aren’t more the merrier types, and that’s fair enough, but it seems a bit sad to block this woman’s adult child from coming to control the dynamic. Is it perhaps you who is making the conversation awkward with her there because you’re less open to new people? Or is it her? If her parents are nice surely she’s alright too? And unless it’s a swinging dinner party, what can’t you discuss in front of her that you would without her there?

She’s either close to her family and happy to mix with anyone, which is lovely, or she’s socially awkward and hasn’t got many friends of her own. She either wants to break bread with you because she likes you or because she’s lonely - those are pretty decent reasons to extend the invite. But each to their own.

Their dd is 40s and looking to hang around with her parents and their friends, she sounds lonely. I would start getting to know her and she can become a friend too.

And if ops uncomfortable or just doesn't want to invite an extra person that's absolutely acceptable!
Am so fed up with the 'beee kind 🥺' manipulative way things have got that makes it acceptable for CF to make demands and have people pander to them because...'reasons'!

I'd do the reply that @EggnogNoggin suggested. I wouldn't accept a self invitation for someone I didn't invite. Freeloaders annoy me!

Then when it's their turn to host, bring along half your family and the cat and the dog and see how they react. 😊

Of course the OP doesn't have to ask anything, and she's not excluding anyone, she just has no reason whatsoever to invit her.

It's astonishing how CF always find a good reason or explanation for their rude behaviour.

That is cheeky. You invited them, not their freeloading appendage.

Personally I would love the daughter to come along, if they wanted her to due to her staying there. I also would be asking about her - Is daughter okay?

You seem uncomfortable with inviting her, Op, so you should change the date with the excuse being that you can easily put off the meal until a date that suits when they do not have guests. If they strongly insist that they don't mind bringing daughter, or leaving her home, then I would cater for the daughter.

No, the onus is on the friend to explain why they have suddenly decided to bolt on their child to every social event! It’s really rude to just assume she can come every time.

I wonder why DD wishes to come? Maybe she has a break up, and needs her folks for support or genuinely likes you both.I would just say yes I think,we read so much about mental health and loneliness its nice to involve her .Maybe you could suggest a lunch date next time ?If the DD is working then she wont be able to come anyway.

This.
If you give in once that is it and it will be assumed going forward.

This type of rudeness would completely turn me off being with them.

It maybe the daughter has had some sort of breakdown and they’re trying to get her to go out in a space they think is comfortable for her! If OP was a true friend she’d be asking if all was ok without expecting an explanation! Trouble with MN is everyone is so judgmental!

I agree with PP and ask if everything is ok with DD. As a mid forties woman I would not entertain a meal at my parents friends house. That said I’m married with my own friends and family priorities.
if this is something fairly new I wondered if the DD has some issues going on, divorce, bereavement, MH issues and her parents are trying to get her ‘out of the house’ so to speak.
if this is genuinely just blurred boundaries you of course have every right to request that the friendship be put back to without additional DD especially as this is your house.
i also agree a firm no we’ll rearrange is much better than a fake we can’t accommodate etc etc.

Set out your stall it will help going forward.

Perhaps the daughter has had some sort of breakdown and they are trying to get her to socialise again. OP just needs to ask if all
is ok with the daughter, but to exclude her is plain stupid!

Best response. Nice and clear but gives them the option to adjust and remain just the 5 of you

Trouble is because you've invited a single over, they probably thought their DD would make up the even number (so beloved of dinner party hosts). You cannot say 'we just wanted to see you both' if there's another person involved (even if the couple do want to see this person)

I’d go with a combination of the above suggestions…”Hope everything is ok with dd, sounds like she needs you around at the moment - no worries we can reschedule for another time when you two are free” or similar.

Give an inch, they’ll take a mile. Don’t agree to it. If they’re “offended”, that’s a them problem. It’s bad manners on their part to suggest it.

I agree with this - a pattern is emerging of their DD always being present.