Is this something to worry about a lot?

Worrying isn't going to help, but your mother's abuse of alcohol and poor diet/sleep habits are concerning. There's no saying if her memory issues are because she's drunk or related to a more sinister pathology...or a combination of the two. Does she have a primary physician and, if so, do you know when she was last seen? It's very common for people to self-medicate with alcohol for depression...but it's a very poor "fix" since alcohol is a depressant. If you can convince your Mom to go for a check-up, I would strongly encourage that. Your suggestion might be better received if you approach it as a genuine concern about her overall health, instead of saying you think she has dementia and/or that she's an alcoholic.