As long as the food is about the same carb percentage, it shouldn't matter what flavor it is (unless your cat is allergic to a particular protein source)
There's nothing special in the "prescription" foods and the ingredients are actually pretty awful.
What I see is that she got down to 30 on the 1.5...….that calls for an IMMEDIATE reduction in dose!! You should be dropping down to 1.25U
Anything under 50 on a human meter is a reduction
She's dropping too low and her body is trying to compensate by releasing stored sugars and hormones to bring her back up quickly (we call it bouncing)
Bounces can last up to 6 cycles so you need to hold that dose until those sugars and hormones have had a chance to clear and you can see how the new dose is doing. (unless she were to drop below 50 again)