Hi ,
There is a Jean Copland 45 born Monymusk , Aberdeenshire on the 1851 Census transcription at freeCEN , status given as widowed.
In 1841 Jean Mennie 30 is noted as independent , with 2 children aged 5 and 10.
Can't see any children born after 1836, so it looks like Alexander died before 1851 and possibly before 1841.
ev