For newly diagnosed cats yes, when you get a test under 50 (if you're following Tight Reg) you can decrease by .25u. If you start seeing that Marmy can't hold the reduction, ie, her numbers trend back up after the reduction, then at some point you have the option of going to one of the other methods of reductions.
One option is to let her go 3 times under 50 before you decrease her dose by 0.25u.
A second option is to just shave the dose a tiny bit with each dip under 50.
The important thing to note is that this isn't a mix and match system. Don't let her go below 50 three times and then just shave it. That sets her up to be overdosed.
When you reduce the dose the goal is to have the numbers continue to stay in green. If you reduce the dose and her numbers don't continue in green you would call that a failed reduction and immediately go back up to the last good dose. There's info on that
here.
You're at about 6 months since diagnosis so I think if you want to choose one of those other options, you could. She's been stuck at the "1.25u isn't enough, 1.5u is too much" for a little while now.
That's all assuming you're following Tight Reg, which I think you are. Would you put that in your signature line, please, to help make sure you're getting advice that's appropriate? thanks!