After looking at the as I wondered about the dry food too.
Is lily eating dry food at 22% carb on a regular basis? Or is it just the contraband she gets her paws on?
A recent experience taught me a very valuable lesson, we were away on vacation and a friend ,house/pet sitted for us, George was recovering from dental surgery, he was very poorly, he's been in remission for two years, since his FD diagnosis he's been on a strict LC wet diet, and so have my 3 other house cats and two outdoor farm cats. Whilst we were away I got the petsitter to feed the outdoor cats kibble, leaving it on a window sill out of reach from George, or so I thought......
In his recovery his bag was doing really well low blue/green, until one morning when my friend tested him and he was in red numbers, she contacted me in a panic. After talking to her we concluded that when she had let him out into the yard he must have got into the kibble, he was placed under house arrest and low and behold his big returned slowly back to normal without the need for insulin.
Long story short, even the occasional kibble could be playing havoc with the numbers. In your shoes I would try to transition the other cat onto a low carb wet diet, in the long run it will be healthier for your civie, if he's a real hard core kibble addict, then it might make sense to look at a low carb dry food, there are some out there, then at least it won't mess up Lily's numbers to the same extent.