Hi Drifty
On Ancestry, search trhe Card Catalogue
For Title put Poor
You will see
London, England, Poor Law and Board of Guardian Records, 1430-1930
Click
On the Right hand side in Borough, select Barnet
In Parish or Poor Law Union, select Hendon
In Record Type, select Religious Creed
The last entry is
Egware Workhouse, 1913-1920
which is the Creed Register I was going to try to look at in LMA
Click to see the images
However, as the only entry found for Mary Ann was the Oct 1913 discharge, it looks as though she didn't return there between 1913 & 1920, if at all
I don't know of anything else that would help at LMA but if anyone comes up with something, I'll have a go