I think you're holding the dose too long. She's been on the same 1.5 unit dose for over 3 weeks. Generally, you don't want to hold a dose that's not getting her where you want her too long because the body gets used to being in higher numbers even though you're giving insulin.
I'd increase her to 1.75 tomorrow.....also, be sure to always get at least a "before bed" test on every PM cycle. Sometimes these kitties can do some crazy things during the night!
Just a suggestion.....any time you get a test that's really unusual for what you expect (like the 157 on the 20th) it's a good idea to grab a quick re-test just to make sure it was a valid test.
Have you read the "sticky's" at the top of the
ProZinc group? Lots of great information there as well as explanations of dosing methods