Sorry this took so long - your friend is right, there's not much authority on this stuff. The 100-300 range was easy to find, the normal levels took a lot more searching! Here's some sites I found:
http://www.sugarcats.net/sites/harry/bgguide.html
http://nmnm.essortment.com/felinediabetes_rjdr.htm

Surprisingly, none of the larger vet school or clinic web pages had the exact figures.

Maybe because "normal" would vary depending on too many factors. Humans test their sugars upon rising in the morning, when it should be 65-110. They also may test right after a meal, when it may be up to 150, or an hour after a meal when it could be as high as 200. But these would all be considered "normal".

But if you throw out a generalized statement like "normal can be as high as 200" then it tends to sound like a fasting blood sugar taken first thing in the morning can be as high as 200, when in fact that is way to high for a fasint BG.

Of course, you have my curiosity up. Why does your friend want to know this?