In my opinion, Linda was free the moment she stepped off the Flint property and escaped the abuse of Mr.Flint and is overly-cautius wife. But technically she is free when Mr.Bruce buys Linda her freedom from the Dodges. Linda seems to have the same viewpoint, she feels guilty when Mr.Bruce buys her something she feels like she already has. Even after Linda is free she doesn't feel that her troubles are over. She it still forced to cope with prejudices in the north, even if she is free, she has not escaped the hate that still follows her around.