Anonymous wrote:If it happens literally a few times in a year max, it's only a few minutes, you text her as soon as it becomes apparent you will be late, and you apologize profusely, I wouldn't worry about it.
If it's happening once a week, then you need to leave work earlier.
+1
And after apologizing profusely you say thank you. If you feel you were far too late (let's say 30 minutes instead of 5/10) or it happens for the second time that week you buy her a $10 Starbucks gift card on the weekend and give it to her as a little thank you. Or you let her leave half an hour early next Friday to compensate the extra time worked.
In an otherwise good and healthy au pair - host family relationship being 10 minutes late two times a year is not a huge issue (I am an ex au pair... I promise it's usually not a big deal), especially if you usually schedule to be home 10/15 minutes before her shift is over. A mature au pair that otherwise feels she is treated well and fairly (e.g. if she shows up 5 minutes late once because she was stuck in traffic you will suck it up as well) will not hold being late <10 minutes twice against you.