Dober večer. 
Yes it does. When you are writing that “vi” is written with the capital to make sure it applies to one “highly respected” or unknown person to you. If you use “vi” without capital then it applies to more persons regardless you know them or not. However it’s different with duality, but I wouldn’t get into complications with that here.
As you are a man and she was a woman this was even more embarrassing because saying to unknown woman “Kako si.” can really be interpreted very wrong way. It’s less stressful if it would happen in relation of man to man conversation or woman to woman in that matter. So I can perfectly feel how you felt. But since she picked the things right way, explaining you the difference (although in a bit awkward situation) it wasn’t such a disaster though.
I have to say that we who are using this difference in “you” against “You” ("ti/Chi) are in slight advantage here though knowing immediately what actually to use in certain occassions.
Well in general we tend to be friendly. Although we all more or less speak at least English we’re always very happy to teach people some basics of our language especially if this is “in the wild”. That’s why I didn’t hesitate to speak Welsh while in Wales. The best way to learn even through the awkwardies we make sometimes.
Hmmm … where was I that time? - hehe Probably not with SSiW yet though.