Back on March 1st (1/3/2020 your date format, 3/1/2020 US date format), you had that BG of 2.8 mmol/L (50md/dL) and you reduced then.
Time to reduce now. Back down to 1U for the PM cycle on March 4th (4/3/2020 in your date format, 3/4/2020 in mine).
Those lows are why mid-cycle testing to find the nadir is so important. Without that, who knows how low Betsy's blood glucose would have gone.
Some cats can be more "sensitive" to insulin when they drop that low. Please monitor closely for the next few days if possible.
Was Betsy's appetite good today? Did she eat ok, about 20 minutes before you gave her the insulin shot?
p.s. I don't think the recent dates on your SS are correct. We entered a new month a few days ago, but you are still typing 02 for the month. Like we do when we go to write out a check and forget what month and year it is.

Leap day threw me off, since my old digital watch did not know about leap day this year. Kept telling me it was the 3rd of March when it was only the 2nd.
p.p.s What does the vet think about Betsy's BG numbers and the dose?