The change to the SS looks good! Thank you for doing that.
Humulin can drop the numbers really quickly, so it's definitely harder to get a good dose that will not send your kitty Sarah into hypo territory. It does look to me like you could go up a bit in dose, up to 1.25 at least, maybe up to 1.5.
One step that can help with the BG numbers with Humulin, is not to feed after the insulin starts to wear off. So no food after +5 or so can be helpful. That's because, once there is not enough insulin left, the food will simply raise the numbers even quicker.
I do see by your SS, that you are currently only feeding twice a day. Would it be possible for you to split those meals up into smaller portions, 2 for the AM, 2 for the PM? Feed portion 1 the 30-60 minutes needed before the shot, and then the next meal an hour or so after the shot?
That way, we are trying to have insulin available when she has eaten, but also not put too much of a strain on her body all at once with feeding her the food all at the same time. Spreading the feedings out a bit instead, can moderate the steep curve.