When I posted that the rejection was based on my first draft where I didn't understand the need to establish "notability". I did some research into newspaper articles where her work was reviewed and added three references.
You can see my latest attempt at
https://en.wikipedia.org/wiki/Draft:Margaret_Hamer
However this has been rejected as having not sufficient coverage (apparently you can't refer to other Wikipedia articles to establish notability)
If you can come up with any reference books that discuss her contribution to children's literature I would happily work them in and give it another shot. I've found a few Google Books but they are pretty well all books authored by her or references to characters in other books named "Maggie Browne" such as the one in Elizabeth Gaskell's "the Moorland Cottage"
BobC