Coincidental cousins

My mother came to England from Ireland in 1946 and married and settled here in Devon. One of her brothers also moved to England and lived in Roehampton. I met his daughters when I went to Ireland for a holiday when I was about 10 and they were 11 & 9. When I was 18 I went to London for the first time with my then boyfriend, a Londoner. We only went for the day, saw a football match and met up with his friends at a club in a converted mill. I saw a girl across the club and said I thought it was my cousin, even though I'd only met her once but I never approached her. 20 years later my cousin and I met again in Ireland, and in the conversation she asked if I had ever been at this club back in the 1970s. It seems that she saw me too but we never approached each other as we had felt it so unlikely and she'd always wondered. Incidentally when we chatted we found that we both worked for the same branch of a government department, had joined in the same year and did the same job, she in Cambridgeshire and me in Devon.