Carol that photo manipulation certainly made her eyes look less creepy! And a date of the 1860s would make more sense if it is indeed the two youngest sons.
My apologies on the death date - it was April 1885 not 1888. Apparently, there is still a gravestone at St Gwynog's (I haven't seen it in person, and have only a transcription not a photograph, annoyingly) that says:
In affectionate memory of/Sarah Smith/of Bellan in this Parish/died April 9th, 1885,/aged 78 years./He is the Friend in Jordan's river,/Me from sinking He will keep/Seeing Him is past rejoincing/Though the waters are so deep.
This also tracks with the civil death index record, so I'm as certain as I can be that this is the correct Sarah.
Thanks everyone for your help and opinions. I still think the picture is rather creepy even if she's alive and well - I don't think I'd want to cross her in a dark alley, is all I'm saying.