Are neighbours being rude?

I think I might let things rest for now. Everyone is going to be out a bit less over the winter, and by spring she may have a bit better measure of her neighbours.
It's also a bit unclear from your post as to how much & how often, and also whether your daughter has got to know them much.
If I was putting out the washing / picking some herbs/bringing in some logs and 2 good old friends called across to each other about something, I probably wouldn't bother too much - though I'd say 'Hello!'
But if I was sitting out in my garden and a full conversation was going on, I would feel excluded.
Has she already taken a chance to invite neighbours in - for coffee / hot chocolate on Firework Night / find out the local etiquette for Halloween? All opportunities to become part of what's going on, or just to know where you stand.

In your daughter's place I would start by jokingly saying to these neighbours when they are talking across her garden,

"I feel like an eavesdropper with you two talking across my lawn, come in and have a coffee, so I don't need to feel I am intruding on a private conversation."

If they don't take the hint, she can be blunter the next time.

Something along the lines of "Don't mind me, I am only hanging my washing out in my garden."

Has she moved to another part of the country.

Having moved around a bit, I found there were very different ideas about how “private” people should be.

In the London suburbs I wouldn’t have talked to a neighbour in a garden. We just pretended that the other person wasn’t there.

Where I live at the moment complete strangers stop and have a chat in the street or pass comments to each other. My neighbours often chat across my garden and would think I was really off if I didn’t join in or at last wave at them.

If they’re lovely otherwise I think it’s probably just a different social standard.

But if it bothers her, a fence I guess. Be prepared for the person whose garden gets put into six foot of shade to be unhappy though. They’ll probably be as unhappy with what their neighbour has done as your daughter is now with with them.?

A trellis with a planter is easy to move around and climbers will grow quickly to cover it - or use it for runner beans next year.

I have bamboo in pots that get moved around to strategic places too!

I don’t think I see this as a problem to be honest why doesn’t she go out and join in she could put up a barrier but that’s just going to alienate her I miss that so much when I used to live both on a council estate and in service quarters we would pop into each other’s or chat on the Green outside but since living here although I love the house and location there’s no one to chat to no one visits or pops in ….but Im used to it now

I wouldn’t like my back garden so open that everyone can see everyone and can chat crisscross to one another, I’m a friendly person but I still like to have my privacy in , and out , of my own home , so , even though I wouldn’t put up a six foot fence as that can look unfriendly, I’d certainly consider hedging or something to break things up a bit .
There is also local park or shop where one can have a catch up with the neighbour’s if you do feel like a chat .

I think a sudden enthusiasm for a tasteful tall trellis in just the right spot is a bright idea rather than "making a point" with 6 ft fence unless she wants that.
I do have 6 ft fences but thats peoples choice round here and gardens are big tho.

The I'd find that intrusive. If I was going about my business in the house or trying to relax and could hear them shouting across my garden to each other I'd be well miffed too. It'll probably all settle down when the excitement and novelty of living on a new estate wears off.

I had this problem or rather my neighbour did for over 20 yrs.

I am at one end, another neighbour next to me then the chatty neighbour(who I must admit was great but overbearing when my dh died) she would converse ove the middle neighbours garden, the middle neighbour hardly sat out as was fed up of it all. the missdle neighbout attached some trellis on top of the 4 ft fence, but the far neighbour complained and only allowed it on 2 of the panels.

The chatty neighbout has now moved and peace has resumed.
maybe plant some conifers (in tubs) they grow very quick and you could postition them where ever, also they do trellis with like a little box attached and you could grow some lovely clematis, move it around etc.

Get a bigger fence and put climbing plants up it. They are being rude and taking advantage of her. How can they ignore a new neighbour and not make her feel welcome?
Although on saying that I have been asked into three houses in our village for a coffee and a craik in ten years. I have never been invited into the house we are attached to, they are very friendly if you are out on the street or garden and most villagers stop for a chatter.
I think a lot depends on if friendship groups have been formed before you move in. Though it did not apply when I lived in the North East they were so friendly and welcoming.

I should add that where I live now we are in a row of cottages in gardens through which one has to pass to get to your own patch and front door - I love the vibrancy and sociability this brings but am aware that this might not suit many people. Being hidden away behind a 6foot fence would be my idea of isolation.

Perhaps when she settles in and gets to know everyone she'll enjoy joining in with the conversation.

I lived in a new build estate where neighbours would lean out of windows, cross the road or come onto your garden for a chat...at first it seemed odd and intrusive but when I got to know everyone it was lovely and made for a fantastic community spirit.

How awkward... you say she has lovely neighbours, so why aren't they including her in the conversation? I suppose it depends whether she wants privacy or inclusion in the friendship. Because I prefer privacy in my own home I would put up a 6 foot terrace and cover it with climbers as I would find this behaviour unacceptable... she'd probably better do it sooner than later and say that she loves greenery around her, rather than fall out with neighbours , if that's the route she chooses .. they might become good friends though.

It wouldn't bother me in the slightest. People are allowed to talk to whoever they like. It is a bit thoughtless of them if she's in her garden though. Definitely invest in a bigger fence

If I was inside my house, I dont think this would bother me, but if they were doing it when I was in my garden, it would make me furious. It seems both inconsiderate and very rude.

Being a nosey person, I would actually enjoy if ?

She cuould put up a six foot fence on the side that she is responsible for.Nothing necessarily expensive, trellis and then plant some climbing plants, even heavy net between posts.

If the neighbours are talking when she is in the garden, she should just walk up to them and join the conversation.

If anyone says anything, just say, 'as you are conversing acros smy garden and I am in it, I just assumed I must be prt of the conversation and it would be rude of me to ignore you'