I notice there are User submitted trees online which have Viva Bushey married to Percy Seymour Keddy - perhaps contacting them - someone might know about the marriage date etc. They might even know of another child born to her.
I seen your other postings in regard to Malcolm John Murray (your friends father)
Looking at the date of his birth, it would put Viva Bushey as 18/19 years old. In personal experience with the adoption, age and being born in the Maternity home - I find it very unlikely that Viva and this Mr. John Murray were actually indeed married, even though the Registration has Murray as the surname, rather than Bushey as was commonplace for "Bastard" children.
Also you could contact whoever holds the records for the Maternity Home and see about obtaining any records, including non identifying. You can also petition the adoption records even though they are closed as both the child and parents would be deceased now. Sometimes they will make an exception.
As for Viva, I have not seen ANY other Vivas especially with surname Bushey - so I, like you believe they are one in the same.
Also the registration stated "Evangeline Maternity Home" it could very well be the "Home" or the Wing that was for unwed mothers.
Im more than happy to help you find anything possible. Ive faced adoptions in my family and I understand how frustrating it can be.
You can also contact me offboard at firstname.lastname@example.org
. Or even Facebook if you have it