Regarding the Estring:
You can insert it yourself, I do, but unfortunately cannot remove it myself and normally get a GP to do it, one who has some experience of women's health. However, many users can remove their own, I think most can and I am just unlucky. I have no cervix. I don't know how long you would have to wait after surgery. I expect it's best to start off with Vagifem.
All the options can, and indeed should, be used forever, as it is a lifelong condition and will return if treatment is stopped
As to your mother, I don't know of any reason why one could not start treatment for VA in the 80th decade, but you can bet your bottom dollar the average GP would find one, as most are untrained in these matters. Perhaps she could see Dr Newson, it would be worthwhile
JP x