Looks like a needle in a haystack, at least until the Scotland's People centre reopens, when it would be easy enough to look at all the original certificates there.
There are 73 marriages of James Gal*hers in the SP index, and 135 deaths of female Gal*hers aged 20 to 40, between 1911 and 1918.
Depending on how determined you are, you could make a note of the names of all the 73 brides, and then search for each of their deaths using both their maiden and married surnames in the search.
For example James Gallagher amd Mary McMenemy were married in Glasgow in 1911, but there is no record or the death of Mary McM*n*m* or Gal*her between then and 1918. If you do this for all 73 there will be only a very short list left, and you can then check the marriages.
If course this does not work if the wife died in England, where as far as I know the certificate doesn't even name the spouse of the deceased, let alone her parents. But I had a look at FreeBMD for deaths of Gal*hers aged 20 to 40 in Northumberland between 1911 and 1918, and there are no obvious candidates.