Hi Sue
I like your suggestion that the enumerator for the England 1911 census thought he heard Port Erin if Annie had said Port e Vullen.
In 1901, when Annie's birthplace was recorded as Ramsey, the scenario could have been that she told the enumerator "Isle of Man" who then pressed her for a town or parish. She could have been reluctant to say "Maughold" in case he asked her how to spell it, so instead gave "Ramsey" as being the nearest town, which I see from the map is very close to Port e Vullen.
If this were my own family, I'd send for the marriage cert of James Thomson and Annie Caley to see what John Caley's occupation was given as. If it stated something quite different from sailor/mariner, then we could assume that Annie wasn't MAC b 1853 Port e Vullen. But then even if it did say sailor/mariner, that wouldn't be conclusive proof that Annie was MAC b 1853 PeV.
Jean