Hello:
Could someone please provide the source for Lady Elizabeth STUART WALKER (https://www.wikitree.com/wiki/Stuart-706) being the child of Ruthven?
The only source I found was able to find was Find A Grave (https://www.findagrave.com/memorial/51088809) Which indicates James Stuart (https://www.findagrave.com/memorial/11199625/james-stuart) and Anne (Campbell) Stuart as Elizabeth's parents.
Peerage.com does not give Elizabeth as Ruthven's daughter.
You are right to suspect that this is unsourced wishful thinking - it seems extremely unlikely that the legitimate daughter of a Scottish lord would take her mother's surname.
There is a different version of the story that connects Isaac Walker to another noble Stewart family that supposedly escaped following Culloden - debunked as early as 1927. https://archive.org/details/stewartclanmaga00incgoog/page/n242/mode/2up/search/isaac+walker
