Hikari had a child out of wedlock and that was a disgrace in her country. Then her child died and she became a mail order bride with a shameful secret that her husband used to control every aspect of her life. She was afraid of him and did not know enough to get help or leave. She sacrificed her happiness and any real relationship with her daughters to keep some peace in the home, and when that failed she was still afraid to disobey her husband in any real, meaningful way. Her daughters were somewhat shielded from their father's cruelty because of this - until she could no longer protect them,, but they could leave, they could make their own choices and live their lives as they chose.
Another big difference is that when Rachel became pregnant out of wedlock her baby daddy married her and all was well, unlike her mother's situation. Both Rachel and Hiraki were ashamed of things in their past that they hid from their children.