Her number is to be expected. They bounce. In very general terms, it means when they body perceives a level that is lower than it is used to, or in her case, too low, it releases extra sugar. So the next number may be higher than expected. i wouldn't give a larger dose for this higher number because you could end up back in this roller coaster of too low/too high. You might give 0.5 minus a few drops , assuming you can get tests early in the cycle and 5-7 hours after the shot, and that this won't mess your schedule all up as you will need to give insulin 12 hours from now. If it will, I'd skip for now, shoot a little early tonight (assuming her number is high enough - which it is likely to be) and start over at a low dose, monitoring carefully. If you skip today, you can shoot when you want this evening, on a schedule 12/12 that will work for you. (Again a lower dose) Then another shot 12 hours from then.
I would be encouraged. She went low on a tiny dose of insulin so going forward, she might continue with a pattern of nice numbers at low doses. Your job is to monitor her levels, keep her in safe ranges and work on getting her regulated.
We prefer home testing. You are more on top of things and it eliminates vet stress. We know stress raises levels and most cats are stressed at the vet.
Does this make sense?