My DD has been on one day sleep since 10 months. DS was a bit better at about 14 months!

I found with both of them things were much easier once we settled down to one sleep. They slept better and it was actually easier to plan around going out etc. Sometimes during the transitiion it's helpful to do one sleep one day and two the next, then one and so on. I don't think that's inconsistent in terms of confusing them, it's just helping them transition more easily.

I think it sounds like you're reading her right. And I reckon a bit of grumping in the late afternoon is pretty normal! Earlier dinner might help on those days?

And - I didn't go out anywhere we'd be driving back late morning - or you get that fall asleep in the car like you described!