Hello, My Great-Grandmother is proving difficult to find!

Her name was Mary Ann Lawrence and we believe that she was born around 1891.
She married Thomas Arthur Cryer in Gabalfa, Cardiff in 1911.
She had at least 13 children including her youngest, my grandmother Eileen.
She died on June 28th 1976

What I am most interested in is her parentage. I've hit a brick wall since my only source of knowledge is my mother who only has childhood memories.
She remembers childhood visits from a great-aunt Nancy and possibly two other great-aunts who may have been called May and Phoebe.

There is a family story that she was the daughter of a gypsy and was born in a workhouse in Merthyr though nobody is sure that this is true! I am hoping that somebody may have access to some sort of records which could possibly help me to confirm or deny this family legend!

Like I said, I am most interested in finding out about her ancestors, but I would greatly appreciate any crumbs of information that can be found relating to her!

Thanks for reading!
Lucy Lavelle