The difference for Evianners is that, having lived in Europe for so long, she will have not had any dealings at all with Imperial weights and measures. In the UK we are exposed to both. Cars dials have miles and kms, tape measures have both too and we can change our personal weighing scales to kgs, st and lb or just lbs. In Europe everything is just in metric with no choice.
I must admit living abroad I use both but if going on a journey I still convert kms to miles to see how far it is. When I start it's 160km to Porto so its 100 miles and when it's down to 72km its ÷ by 8 and x 5 so 45 miles. But when returning ro England one should accept that not everything is going to be metric.