I don't have a problem with the wall, well I do, it's hardly neighbourly is it, and we have had many a chat over our low wall 
But anyway, that is what she is doing and I respect her decision.
When she first talked about it I said rightyo, but we will be removing all the stuff between us first, right?
We have slabs, some old posts (inc the old barbed wire) and a hedge.
We agreed that it made sense to work together to do that first.
Now the foundations are being dug out and all the guff is still there, including the hedge which is on their land.
I went to speak to them about removing everything first, that having been what I agreed to.
But they, the FIL mainly, and the DH, decided to just bring the wall 6" in to their side in order to avoid all that.
ie leave it all on my side of their wall, hmm
That would then mean that I am left with the 6' wall, then a bush, then my slabs, with about 3" to play with to get all this back out!
Just not possible, no wiggle room. The slabs go underground by about 12".
It would make so much more sense to pull it all out some whilst there is room to do it.
The FIL was NOT happy with my input as they already dug the foundations and pulling out bushes would then knock everything back into the trough they had just dug.
I see his point, however, should he not have thought on that Before he dug the founds?
We also have a big tree slam in the middle of the party line.
That would leave me with a new wall, an old bush and a big slab pressed up hard against the tree trunk!
How on earth would I EVER get that sorted??
Am I being unreasonable in being quite cross, and worried, about this turn of events.
My DH works away from home, my Dad has hurt himself, I have no way of removing them myself!
I can't just sit back and let them build their wall, leaving all that ugliness for me to Not be able to deal with at a later date.
My sis says they don't Have to deal with it, legally.
But really, why would they do this