@rmclean2,
What's the big deal? I live in a city of over 3 million people and I sometimes run into people I know - far away from the place I normally see them.
I've travelled to New York and run into people I know there.
Travelling back from Europe once, a friend of the family randomly ended up being in the same row on the plane.
It's no big deal.
Now I'll admit I thought it was a bit weird to run into a friend's ex-husband on the subway. He was on a two-day visit from another continent.
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Do you ever say anything to your neighbour when you see her? you might find out you have a lot in common - and that's why you end up in the same spots occasionally.