Hi Caroline,
I think this is them in 1841. Isabella's age looks a bit suspicious so possibly a mistake there. All born Renfrewshire.
Address: Rankine St, Johnstone, Renfrewshire
Robert Steele, m, 34, coal miner
Isabella ", f, 51, -
James ", m, 15, cotton piecer
Mary ", f, 13, cotton carder
Robert ", m, 11, cotton carder
Archd ", m, 7, cotton carder
Isabella, f, 20, cotton beamer
Like you, I can't find a death for Isabella. Have you checked for re-marriages, or deaths under her maiden name?
hume24