Dopplegangers?

Years ago I saw my former best friend from school in town. She moved away a year or so before. We were in our teens by then and had been very close for years, I was bridesmaid at her sisters wedding. I was so pleased to see her! 'Hello' I called out but she just looked at me. I said 'It's me!' Her eyes were totally blank and her response was 'Sorry but I don't know you.' At that point the penny actually dropped and I apologised and made a hasty retreat. She said that it happened all the time and I could believe it. I have to say this girl was the exact double of my friend - hair, face, everything. They say we all have a double??