I haven't found a marriage but was told she married a Christensen
Hello Annie,
You say you were told that she married a Christiansen. Presumably the family had no connection with the Christiansen family later?
I have seen an interesting marriage:
1943 Mary F Christiansen marriage to Louis E Tinard.
Then a death
1956 Bootle Mary F Tinard.
Does any of this ring a bell?
Mary F Tinard is in 1939 index so they must have been together before they married.
There is a Sarah McBride (Christiansen) also in the same household.
Free BMD shows a birth Sarah Christiansen, 1919 with mother Thompson.