I would be advising her to move most of it out of her current account and into savings, to begin with.
If you don't like talking about death and wills and the future, then you can't really expect her to either.
As to whether it is right for you to ask for some help, now, I think that depends on lots of things.
Some posters have inferred that £50K is all she has, but if she has that sitting in her bank account, and thinks £100 for a midweek lunch for two is an ordinary week of spending, it does sort of suggest that she has considerable wealth.
Personally, I would rather help my adult dc out as much as I can when I am alive, than sit and watch them struggle if I had a lot of money that was going to go to them when I die anyway. If your Mum has never had to struggle, she might just be blissfully unaware of your struggles.
Yes, I know lots of people will say it is the mother's money, and obviously it is, but many of us feel we wouldn't want to see our dc struggling if there were something we could do to help them.