It is if the insulin is at too low of dose. I recommend raising her to 2U at the next increase. Her BGs are too high consistently. A .5u increase at this point would follow Tilly almost to the letter because BGs are still in upper 200s & 300s often enough at nadir and because she's now getting a larger dose.
I hate to see a cat stuck in the 300s. I know we don't want her to bounce but she's not seeing much movement on Levemir at any dose so far. When that happens I don't think it's necessary to hold one dose 5 days. Once she begins getting 100s, then we can slow down the dose increases.