Diabetic mouse - now what?

Hi,

I wrote in earlier this week about my mouse Guernsey and what I thought was
a possible kidney stone. She got worse that night so the next morning we
went to the vet. She was diagnosed with a "probable" bladder infection, for
which she is taking antibiotics, and also "probable" diabetes. The vet
didn't want to take any blood from her because she looked anemic. Her
urine darkens the ketone stick *slightly*, but they are calibrated for
humans so that could be a significant amount for a mouse.

The vet recommended "more fiber" in the form of Cheerios... but other than
that she didn't tell me how I am supposed to control my mouse's diet.
Currently Guernsey and her 3 cage mates eat a mix of lab block, mouse and
rat food (the stuff with seeds, nuts and corn) and occasionally bread with
oil, veggies, sometimes fruits, although they don't really like fruit.

What should I be feeding (or not feeding) a diabetic mouse? Do the other 3
girls have to change their diet too? Now I just put it all in there and let
them eat what they want- do I have to "feed" them and then remove the food?
Any experience or advice would be appreciated.

Thanks, Meghan