hello Joe
and welcome to TP
what a worry - not a good mix, dementia and alcohol
have you let your mum's GP know exactly what is happening, as she is unlikely to tell the full truth so they may not be aware - and there may be meds that will help
maybe AgeUK can help
http://www.ageuk.org.uk/northern-ireland/
and there are some AS factsheets that may have useful info
NI factsheet: Community care assessment (NI418)
https://www.alzheimers.org.uk/download/downloads/id/1922/northern_ireland_factsheet_financial_and_legal_tips.pdf
I'm afraid you may have to shout loudly at Social Services to get support - helpful phrases are; your mum is a 'vulnerable adult' who because of the drinking is 'at risk of harm' and the Local Authority have 'the duty of care' to support her
there are members here from Northern Ireland - might you add this as a location on your profile so that should they see your thread, they will know you need advice specific to NI
apologies for just flinging info at you
keep posting with anything that's on your mind
best wishes
PS LadyA is right - can you water down any spirits, only give her the mixer without the shot, get non-alcoholic/low alcohol lager/beer, low alcohol wine and put it in the bottle or can she usually drinks - time to get sneaky if at all possible as she isn't herself able to control her behaviour