When your sitter rechecks the number is going to be food influenced by the gravy.
At 161 she is safe and gravy wasn't needed, a better strategy would have been to withhold food and see if she is rising in 20 min, that way you can tell if she was still dropping or if in fact that 161 was her on her way up.
Even if your sitter shoots a reduced dose, the first part of the cycle can still play out as if you gave the full dose.
Can your sitter leave higher carb food out for Millie in an autofeeder.
If Millie is currently not having any other issures, ie she is eating, acting normally, no infections you could get the sitter to shoot 1u, and leave higher carb food out for her to snack on for the early part of the cycle. +1 through to +5. Then take the dose up to 1.5u tonight. The problem with that choice and DKA in the mix, is that it might not be enough insulin and we don't want to court another DKA episode, and she will likely still have a similar cycle.
Can your sitter possibly get a +1 and or +2?
If it weren't for the history of DKA as you are out of town skipping would be an option, but I don't like that choice in Millie's case.