You need to take this to your housing association as they are the owners of the property. Its up to them to take the matter further if necessary.

I agree with Cammomile. You may also get good advice from your local Citizens Advice Bureau

Did the neighbour put up the original fence? even if it is the boundary fence, if she put it up then she owns it and can remove it if she wants to.

There is nothing you or the housing Association can do about her putting up a new fence that in on her land, which it sounds like she did. You cannot put anything on it or paint it. By deliberately putting it away from the old boundary she is telling you in no uncertain terms to keep away from it.

What you should do it put up a fence on the old boundary and ignore hers.

Re the tree - that is wrong. If she cut a tree or moved or pruned a plant on your garden then she should replace it.

Strange thing to do and I agree take it to the house Ass, they will sort this out for you and take action if required such as new fencing. In the meantime do not do anything that could be seen as trespass as the boundary is still there fence or no fence!

How very odd - it's quite common for people, when replacing a fence, to move it a few inches outside what's their boundary, in other words, nicking a few inches of your space. Never heard of anyone being daft enough to give up a foot of their garden to someone else, very strange.
And you're right, if she's removed breeze blocks/sleepers which were retaining higher ground around her garden, she will have a problem later. That, though, is not your concern, really.
As everyone says, talk to the HA before doing anything, but Kildermorie's suggestion that you erect your own fence on your boundary line, leaving the foot of space with posts and orange netting behind it, is a good one. This would cover the area that's unpainted of your house, stop you seeing the boundary marker she's placed there, but it does have one drawback. There'll be a foot of space between two fences where weeds can grow freely, so if you choose to erect a fence, I'd anchor down weed membrane over that foot of soil before the fence is up.

I was willing to pay half for a new fence or the broken one to be repaired,even if it wasn't my nephew that broke it by jumping off it in the snow.until the HA had a phone call demanding that it was to be replaced by them.and my name was given,she even told me that she rang and said she was me but i had a completly diff story.anyway the HA after a visit when she removed the fence and burned it while i was shopping said that it was her responsibility to replace the fence and i was told that in no certain terms that i was not to pay or replace it. considering it only needed to put back the 1 maybe 2 posts and fix the 1 pannel back on.seems to me that some people are very dishonest and when they cant get will do and say anything no matter how low they have to go.even if people who genuinly need help from charity ,social security,grants are going to suffer.
Anyway want to thankyou all very much for your suggestions and advice,i'm very gratefull.
many thanks,
reallyfedupofndoor

I don't think that's the way it works all the time - We have one adjoining neighbour to our left but it is our fence. Just depends on what the deeds to the house say.