Hi Marilyn - welcome to Rootschat.

Strange one, this! Your grandmother's death entry (just the index) does show on ScotlandsPeople. Her full name was Eliza Ann Gordon, maiden surname George. However, I can't see a marriage for an Alexander Gordon to an Eliza George between 1910 and 1920.

Do you have your mum's birth certificate? If she was born in Scotland, the parents' place of marriage and the date would be noted.
hume
Edit: I'm so slow. 