Boxie is right, as one who has to deal with it, a sympathetic play through her GP is the right way to kick this one off......each dementia (could be one of seven major types) has its own characteristics and what is good for the goose doesn't necessarily apply to the gander.
From the appraisals (and probably a CT scan and MRI to determine if there is aby vascular (stroke) damage) they will assess the best route forward. Your b-i-l at home will be important for keeping her there....does he get a carers allowance - one of the benefits along with an attendance allowance for her (£54 a week) and reduction of local taxes?
For example, my mother is mid Alzheimers and Vascular, known as Mixed. Can't remember family except eldest sis and me, can't remember what happened an hour ago, can remember the long term, has issues with what we term sequencing (putting basic tasks together in natural sequence) but has not taken to forgetting where she is or wandering off.........or overtly aggressive with non-family. Yes, she also has issues with losing jewellery, purses and accuses family over those - that is fairly standard.
The Alzheimer's Soc has a lot of info and many of us are on here regulalrly lilac.
http://alzheimers.org.uk/
their password is hard to remember as it has 16 characters......(joke) and remember humour is an important outlet in all of this sad disease.