There is a thread about this nearly every week -- it is starting to rival baby showers.
The French say "Lou-ee." Americans (and many others) say "Lou-is." (We don't say "Lou-is" if the person is obviously French.) Why do British people get so upset about this? After all, you pronounce the "h" in "herbs", and the "t" in "filet" and "valet." There just isn't perfect agreement about which words we pronounce the French way and which ones we anglicize. It's not a matter of being "yoonique" (at least not in America).
There are lots of names, like Robert, Thomas or Charles, that are spelled the same but pronounced differently in the 2 languages. (And I would argue that the names Sophie and Natalie are not pronounced the same in the two languages, either -- English people don't say So-PHEE or Nah-tah-LEE. You don't say Lou-EE for that matter, either.)
And don't get me started on Pops.