What you are running across here is a difference in the pronunciation of names which is historical as well as cultural.
Between 1200 and 1600 A.D., the English language went through what's called the "Great Vowel Shift". One of the first changes was that the "long" sound represented by the letter "i" changed from "eee" to "eye". Back when Lady
Godiva herself was living, her name was probably pronounced with "dee" in the middle. But by 1600, native English speakers would have been using the "go-DYE-vah" pronunciation.
But most other European languages kept the "ee" sound for the letter "i". During the 19th century, English speakers, especially in the USA where there was lots of immigration from continental Europe, began to get used to "i" in
names as being pronounced with the "ee" sound, as in other European languages. Back in the 1700s
Maria was pronounced "mah-RYE-uh" in English. I myself had a great-great-grandmother from Tennessee named
Maria, and her name was always pronounced that way. But during the last 150 years, as the average American has been exposed to so many examples of how
Maria is said in languages like
German, Spanish, Italian, and Latin, the normal pronunciation of the name
Maria in English has gone back to "mah-REE-uh", and we've had to create the alternative spelling
Mariah for those who still want the name pronounced in the 18th century way.
Because the story of Lady
Godiva has been told for so long, the pronunciation of her name in English has been "stuck" with the "eye" sound favored in the 18th century.
Sunniva, though it was originally the name of an English saint, did not survive in use (or regular discussion) in English. I am sure that when an English speaker around 1800 would have seen Sunnniva, they WOULD have pronounced it "sun-NYE-vah". But today, we are so used to names like
Lisa,
Tina,
Louise, etc. being pronounced with the "ee" sound that the tendency is for English speakers to assume that sound for "i" in any new name that they come across. It is only names which have been constantly talked about since the 1700s, such as
Godiva and
Ida, where we seem to keep the "eye" sound at the present time. And so most modern English speakers are probably going to look at
Sunniva and first try something like "sun-EEV-uh".
I would assume that most English speakers when looking at Linniva today would tend to say "lin-NEE-vuh". 200 years ago, they probably would have said "lin-EYE-vuh".
Of course, if you want to know how Linniva would be pronounced in some language other than English, you would need to consult someone fluent in that language.
Here is a link to a site about the Great Vowel Shift:
http://facweb.furman.edu/~mmenzer/gvs/