There isn't really a recommended testing interval. You will have to learn how Kit reacts to increases. Some cats react right away, some don't until 5-6 cycles after the increase. The depot has to build up again. A good test for you to get is the +2 test. With Lantus, it often indicates how the cycle will go. A big drop from preshot means an active cycle that needs closer monitoring. A similar number to the preshot means a typical Lantus curve, but can still go down. A higher +2 means a quiet cycle - good for errands and catching up on sleep. Note that these guidelines are ECID - they work for a lot of Lantus cats. Not mine of course.

Her onset was later than typical - never did like to follow the "rules".

So for now, try the +2 and use it as a guide to how often you'll have to test. Take a look at Kit's spreadsheet on Lantus - are you able to predict what type of cycle he had with those early tests? Unfortunately you did get an early test on the PM of the 11th, but you will have plenty more time to build your data. Once you start seeing more blues, the patterns will become more obvious.
The what to do with a lower preshot depends on a number of factors. Your experience level, the amount of data you have showing what Kit does with a meal - I knew Neko went up around 30 points with dinner, your ability to monitor, and whether you've got high carb food and plenty of test strips should things go sideways. What also comes into play is when a can nadirs - my girl often nadired near shot time, so her numbers then would naturally be lower. Similarly her onset was later, so I knew she'd be going up for a few hours before the next insulin dose kicked in. Learning onset and nadir can be useful tools, though nadir can move around. The best guidance I can give, if you aren't certain what to do, is ask for help. Also, take a look at other posts, try to find someone else who is relatively new and in the same situation. My first low number, no one was around to help, but I'd read enough and new what the suggestions would be.