Edit: just purchased the certificate and it's correct
Good.
Does it confirm that her parents were William McD and J*an* Jardine?
And does it say whether she was married to, or the widow of, John James McD?
Have you checked the two deaths on SP of John James M*cDonald born 1867 plus or minus one year? I think the one in Milton (Glasgow) is more likely to be yours because https://libindx.moray.gov.uk/mainmenu.asp says that the one who died in Burghead on 6 October 1932 was born 1 May 1867 and married in Elgin on 10 December 1887 to Margaret Ann Ogilvie.
Apologies for the late reply, we've had no electricity since the storm on Saturday!
Her death certificate confirms her parents were James McDonald and Margaret McDonald nee Carson. It also states she was married to John James McDonald - electrician. Their son John James McDonald Jr was present at her death.
I purchased the Milton death record for JJMC - electrician retired widow of Jemima McDonald. Adding more confusion into the mix it states his father was William McDonald - Horse Dealer (I have William's profession as a weaver, then later on he became a Carter) and Agnes McDonald nee dunlop. His son JJMC Jr also present at his death.
I believe his parents were actually William, correct, but his mother was Margaret McDonald nee Graham I don't know who Agnes Dunlop is I have not come across this name before.
If it is correct and he married his half brother's daughter I suppose it wouldn't have been talked about. Perhaps their children never knew?

William McDonald John James McDonald and James McDonald's father was married/partnered 3 times.
1st Wife Jane/Jean Jardine they had the following children:
Elizabeth McDonald 1828-1856
John McDonald 1831-1865
Jane McDonald 1833-1906
Mary McDonald 1835-1862
James McDonald 1838- 1865
Father of Jamsie/JemimaJane/Jean Jardine must have died - don't know the date.
He then married Margaret Graham when he was 59 years old 2 Dec 1863.
They had the following children - confirmed by birth certificates from SP
Agnes McDonald 1866-1889
John James McDonald 1867-1962
Married to Jamsie/JemimaMargaret Graham died 1870.
He then married Elizabeth McKay 8 Nov 1870 and died (most probably) in Carlisle at the Fusehill Workhouse in 1873.