I worked in the book trade until six months ago and have a lot of experience with books like this.
In a nutshell, unless your mum is a fantastic writer and has written a book that would sell nationally, your market is going to be pretty limited. A commercial publisher would be unlikely to show an interest, so you'd probably have to pay for it to be published. The Book Guild (formerly of Lewes, now in Brighton) specialises in this area and produces good quality books.
Another option is getting your mother's memoirs published on a website, which would be cheap and could actually reach a wider audience. You may find a friend of a friend who knows about creating websites.
As a bookshop manager, one of my hardest tasks was dealing with people who'd published memoirs and were so excited about it that they couldn't understand why I was less than enthusiastic. However, at the end of every financial year I had to write-off unsold stock and titles by local authors usually made up the bulk of these books.
There are also companies who can publish a few dozen copies to give to family and friends.
My dad wrote some interesting stuff about his childhood and the war. We printed it off, complete with photos, and put the pages in an A4 document folder. It was almost as good as a book and cost a lot less.
If you believe your mum's memoirs have commercial potential, I'd suggest contacting a successful local author - David Arscot. However I suspect he'd confirm what I've said - be prepared to part with a few quid.