Is it, though? I mean, if a city was named, centuries ago, by people who pronounced that name a particular way—and then language shifted in some way and every modern person pronounces the name differently... are the living people right? Or would it be "more correct" to pronounce the name the way that the people who came up with the name pronounced it?
(The Duchess of Argyll would certainly have pronounced the city's name as "Reg-ee-na", given that she named the city after the Latin word for "queen" [to refer to her mother, Victoria], and the Latin word is pronounced that way.)
It's a bit like asking whether the correct name for Saskatchewan itself is "Saskatchewan", or "Kisiskāciwani."
It's also a bit like asking whether the people of St. Louis are wrong to be pronouncing their city's name with a vocalized S.