While she was serving in the shop in 1888, she met Vincent van Gogh, who HAD COME in to buy pencils.
We use the Past perfect for an event that happened before another event in the past
Her parents RAN a shop in the town and she WORKED there when she WAS a teenager.
We used Past Simple for a sequence of events that happened one after another
Jeanne Calment WAS BORN in 1875, in Arles, France.
We use Past simple to talk about actions that happened in the past
While she WAS SERVING in the shop in 1888, she MET Vincent van Gogh, who had come in to buy pencils.
We use Past simple for a single event that interrupt a longer event in the past. We use Past Continuous for the longer event
Fernand WAS very wealthy so Jeanne never NEEDED to work.
We use Past simple to talk about actions that happened in the past
She married Fernand Calment and then gave birth to a daughter, Yvonne.
We used Past Simple for a sequence of events that happened one after another