Why and how does celie's voice change from the beggining to the end of the color purple

She grows up. When the movie or show starts she is a young teenager, probably no older than 13. Then over time she/the actress changes and a female just like a male has their voice changeas they get older.Why and how does celie's voice change from the beggining to the end of the color purple
excuse me?

what do you think of this

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