I hope you're planning on getting another test soon! That's a good sized drop by +3.
Gabby won't let my cat sitter test so I'm very familiar with the drill! I reduce Gabby's dose when I travel. Given that Lulu is currently at 1.0u, I would think about reducing to either 0.75 or 0.5u. If you are confident that your sitter can measure 0.75, I'd lean in that direction. However, it's often easier to have a person who's new to this process draw up a dose that falls on a line on the syringe.
I would also make up a syringe as a sample and use a colored liquid so your sitter has a comparison. It is a huge safety precaution to have a syringe with colored liquid there that way there's no mistaking 0.5u with 5.0u.
The above said, let's see where Lulu's dose is on Thurs. evening. A lot can happen in the next 2 days. On Thursday, could you put a note in your subject line indicating you need help with vacation dosing?