So how were the improvements achieved?
1) I realise now that S was probably just as shocked and distressed as I was when she had the awful and sudden decline. She didn't want to be the apparently helpless person that she seemed to be, so she made, and has continued to make, real efforts to respond to my suggestions, requests, and thoughts about what might help.
2) S got her appetite back, but we don't really know why. I had a lot of help from the dietician to whom we were referred. She advised forgetting everything I'd ever learnt about a healthy, balanced diet and to give S loads of calorie rich stuff - cream, butter, honey etc. It was hard and I had to keep reminding myself when looking at nutrition information that I wanted the calorie count to be as high as possible. Gradually she started to eat more. Breakfast and lunch were thick sandwiches, I tried to establish a sit-up evening meal - with some success - and presented all kinds of between meals snacks. My brother and sister-in-law invited us over once a week for a proper meal and the fact that S usually ate 'properly' there, with minimal help, was greatly encouraging. Gradually things began to improve and success bred success, old habits were re-established and I was eventually able to start reducing the cream, butter and calorie-rich snacks. She has now reached what is probably her ideal weight and our diet is gradually returning to normal.
I'd actually lost quite a lot of weight with the stress of the decline. It was quite pleasant to have a period of eating whatever I liked,, when I liked. Now I've got back to where I think I should be so neither of us really needs anything other than a normal healthy diet. We are maybe a little deficient on vegetables as S, despite being a non meat-eater, is not very keen on most vegetables. But we eat a lot of fruit and S drinks apple juice almost exclusively.
3) I've mentioned the benefits of walking previously. I'm still very impressed by the ease with which S manages to walk at a reasonable pace considering how she was back in the autumn. She talks non-stop and the 'conversation' is often more agitated than when she is at home but when she gets home after a walk there is usually a lengthy period of calm.
4) We're attempting to suppress the herpes virus with aciclovir (an anti-viral medication and the only medication she has taken for several months. There are several posts on the possible link between Alzheimer's and herpes so if you haven't read them already, just put 'herpes' into the search box at the top left. I was interested to learn that the manufacturers recommend a dosage for suppression of the virus and that this can be used for months or years. I originally thought it might be difficult to get a continuous supply form the GP, but he was very helpful. I feel that S has become more aware of other people since we started this treatment but it is hard to prove.
5) We were introduced to a wonderful woman whose working life has been spent in care homes. She's now retired and hadn't worked for a few years but for whatever reason decided to work as a carer for people with dementia. We employ her for between 3 and 6 hours a week. It's very good for me, having time for myself to do things I need and/or want to do. Sometimes I stay at home and keep out of the way. I've also met friends for lunch, been for bike rides, and gone shopping in a relatively relaxed way, amongst other things. This wouldn't be nearly so easy if I didn't have someone who so clearly had an immediate rapport with S and who clearly had the skills and personality to deal with any foreseeable difficulties. From what I can see, S is very relaxed in her company and is always calm and happy when I take over again. So we are both benefiting.
6) Finally, for now, there are the groups and activities that we now attend. The Young Onset Centre proved a real let-down but eventually the admiral nurse and the occupational therapist between them pointed us in the direction of singing, social and music therapy groups. These are all quite challenging for S - she is usually the most challenged participant by far - but, because she is essentially a very sociable person, she certainly appreciates that side of the activities. And other people are generally able to see past the unusual behaviour and appreciate her real personality. She has never shown the slightest reluctance to go to these groups, despite the fact that our schedule is somewhat more hectic now.
P.S. One of the most important factors has been the help and support of S's daughters. One of them is 3 or 4 hours away and now has two young children but she is as supportive as possible. The other one, who lives locally, sees S several times a week and has a wonderfully relaxed attitude to what must at times be quite distressing behaviour from S. It's made an enormous difference to me to have someone who now knows more about S's problems and strengths than anyone else apart from me. I don't know what I would have done if she hadn't risen to the challenge so magnificently. I can talk to her about S from our shared experience and we have learned from each other. Other family members, from both sides, have done all that they can, as have many friends.