Novolin insulin tends to work fast and bring numbers down quick which is why you see the big drop so soon after the shot. The nadir ( lowest number) "typically" is betwen +4-+6 (each kitty is different though) so she "may" drop a bit more. She may also already be at the nadir point but you would need to test again.
If you have any higher carb wet food..something with gravy...give her a bit of that. Retest again and if the numbers are still dropping you could give her a drop of karo, honey, pancake syrup etc on her gums. This should bring the numbers up quickly, but doesn't last long so a higher carb food should be given.
The best approach would be to only give 1 unit at each shot ( every 12 hours) and see how Kya responds to that.
ETA The preshot was so high because of doing only one shot each day. Kya has no insulin coverage for the 12 hours before the AM preshot test. Doing 2 shots daily at 12 hour intervals will keep the numbers from going so high.