Alan, you know we love challenges here on RC

I think now though to move forward on this Mary, someone needs to pay to view at least the marriage cert for Mary to Charles that has been found by Fifer in 1889. Without this you have no idea whether it is the right marriage (likely, but needs to be confirmed) and also further details on Charles.
So, likely married 1889. Missing in censuses in 1891. Looby found a very possible entry for Mary in 1901 working in England and showing as married. Possible entry in 1911 in the Midlothian area for a Mary H Green aged 43. That is where it is at for now...
Monica