Movie name? Mentally Handicapped Young girl. African American family.?

I was watching The Color Purple this weekend and it reminded me of another film set probably in the same era (early 1900s to the 1940s). I remember the details vaguely. One of the characters was a young African American female (very light skinned) who appeared to be mentally handicapped and near the end of the movie she had become pregnant. For some reason I think she may have been made to sleep out back in a shed/ shack separate from the other family members. Ive searched the internet for 2 days and Ive come up empty handed. Thanks for any answers! Even wrong ones :-)