I did it a little bit different . blurred Gaussian twice with 0.5 parms . This got rid of most of the artifacts , hue-saturation filter desaturate , very slight rotate, used colorise to add a tint, added white layer with color (blend) at about 60 % to bring the colour back to where I liked it best, cropped 4:3 . sharpen 35% then individual sharpen and blur to bring out lady next to standing lady. I deliberately cropped the standing woman to show her to be of lesser importance and so hopefully your mum is now the star attraction according to rule of thirds and the composition.
I think the whole picture is very important for history's sake but I thought a nice crop would make a better picture.
NB am working on a small notebook and the colours may require a bit more oomph! Hard to say with my machine.

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