She may spike high, but she may also come back down. Once you start changing the diet, it's really difficult to predict what will happen. Yes, even a small change can have dramatic effects. If you shoot (even a small dose) you could be in for a wild ride overnight. I can't tell you how often you will need to test, it will depend on the numbers. It's likely that the lower numbers will come later on, in the middle of the night, after the dry food spike wears off. Can you stay up all night if you need to?
If you skip, she may go high, she may not go that high. Skipping one shot will not have a long lasting effect in all likelihood. The problem is that I can't predict what will happen....ECID. It is not unusual to have to skip shots when you are transitioning the diet.
Skipping is the safest way to go. I can't tell you not to shoot, but I would skip. Ella will get back on track.
Does she have a history of ketones? I didn't see any ketones on her ss...