Why does Celie believe the little girl she sees in the dry good store is her daughter?

Celie spots a girl who she knows is her own little girl; she knows because the child looks just like her and her father. She remembers that she called the child Olivia. She talks to the girl’s new mother in the store. Olivia’s new mother is waiting for her husband, The Reverend Mr. ______, to pick them up, but he is not showing up, so Celie offers them a lift. The two women talk, and Celie asks how old the child is and what the lady and her husband call her. The child will turn seven in December. The girl has been officially named Pauline by the Reverend and his wife, but because she looks so much like an Olivia, they call her Olivia.