welcome!
I see a few possibilities. As you start to gather more data, it will be easier to narrow things down.
First, Sabrina is responding very well. I know the high preshot numbers can be frustrating, but she's also getting into the 100s sometimes, so that's good.
About this morning's high, there are a few possibilities. One is that some cats have a pattern that we call "high before the break," in which they throw a random high number just before their numbers drop. Seeing it happen one time isn't enough to be able to say for sure that this is a pattern of hers, but it's something to watch for to see if she does it again.
Or, it's possible that today she was coming out of a bounce. Cats can bounce up high after they hit lower numbers than they are used to, or even just from dropping fast even if the numbers aren't that low. The reason is that when the BG drops low, the body's response is to panic and think "i'm about to hypo!" and release counterregulatory hormones to protect the cat from hypo. It doesn't even matter if they are really headed toward hypo, bounces can happen if they drop into numbers they aren't used to. Those hormones can take anywhere from one cycle to three days to clear out. We just ignore the highs and wait until they clear.
So it's *possible* that Sabrina could be bouncing from some lows the evening of 1/28, or maybe even last night. Normally a Lantus curve would have the number at +2 be about the same as the number at preshot. Her +2 that night was lower than her preshot, then the numbers head down until nadir, so chances are she kept going down from there. Also, you can see on Sabrina's spreadsheet on 1/23 that she is capable of dropping down during a cycle, then bouncing back high again before the next shot time. The same certainly could have happened on 1/28 or 1/29, and now that bounce is clearing out and letting her head for lower numbers.
My thought on dose right now is that most likely Sabrina is going to need a bit more insulin to get her into green numbers and help get rid of the highs. Our protocol would call for a dose increase to 1.25 units BID because she has had nadirs in blue. If you're able to get another test at +5 or +6 tonight to see if she hits green, that would be helpful. She'll probably still need the increase, but once they start getting more green then you might want to wait a bit to see if that settles in.
eta: I see that while I was typing my long response, Carl and Sienne already posted!