Hoping I don't fall into a timing trap

mother:

*born in 1911 in Germany (Silesia) *emigrated in 1951 to England *married in April 1951 in England to my British father *as far as I know, she held no other nationality at this time *naturalised in England in June 1951 *now deceased.

self:

*born in wedlock in 1952 in England

I initially thought that I would be able to apply under Stag 5, ground 2, as my mother believed that she had lost German nationality upon marriage, as was definitively the case up until 1949.

However, further research leads me to think I am ineligible to apply as it would appear that she did not in fact automatically lose her German nationality upon marriage to a foreigner at this time.

Is this assumption correct? Am I totally out of luck because of the time period and an assumption on the part of my mother that she could not retain her German nationality?