Just for clarification,I understand from reading your post you live in a detached or semi-detached house,is this right?
If this is the case, the lady has really no ground to stand on,you are free to do as you please IN and and around YOUR OWN premises,after all NO ONE so far has come up with a law where smoking on a balcony is prohibited or indeed somewhere outside.
You make up your own rules as you live in your own house,it would be different if you were living in rented accomodation,then there would be a set of houserules to follow.But again,they can't be set by the neighbours!!
In regards to the compost,it's understandable,should it be placed so she has the view onto it when sitting on her patio or balcony,that this is not exactly a nice sight and thus she can ask ( NOT COMMAND) you nicely to move it elsewhere.
If everything came/was at standstill for the last 40 years in this particular estate,it does not mean that it has to be so in the future as well.To me it looks very much like a case,where someone has a bit of a problem to accept something new.
If this is a close knitted community with lots of elderly people living there,it might be a bit tricky to make them see that other (younger) people have a different lifestyle than them.
Try to find out if there is a so called QUARTIERLEIST,this is a sort of club of ppl who live on that estate and for example organise a Quartierfest,or if the town wants to build a road through your garden they are the ones to start a petition etc etc. It's abit of a mix between a political organisation and a club.
Also as a home owner you have rights,it would be adviseable to join the HAUSEIGENTÜMER VERBAND
http://www.hev-schweiz.ch/
Should you have further problems with this particular neighbour,they have also a judicial service for the members and it might help if they would act as a mediator.
This is the sort of legal side of where you stand at the moment.
Like i said in another post,communication is everything nowadays.
And you did the right thing by going to meet the your new neighbours and apparently ,this lady is well known for this kind of behaviour or maybe being exluded makes her react like a child,in the way of attention seeking,if no one doesn't want to socialise with her.
It might be worth a try to invite her over for a coffee and ask her how life has been over the past 40 years on this estate.Im my experience elderly ppl like to tell about times long gone and suddenly you are not the 'young' enemy anymore,but a person who's interested in her.