I don't recognise my granddaughter.

Forgive me a personal post.
Yesterday my youngest son sent me a text which continued some photos, he had found an account on social media for my granddaughter, and on one of her friends account there was a photo with two young ladies smiling at the camera, one of them was my granddaughter, I sat staring at it for hours, I didn't recognise her.
How has this happened, how can a gran look at a photo and not recognise her own granddaughter?
The granddaughter that I love so deeply is a stranger to me.
Jane
www.bristolgrandparentsupportgroup.co.uk