You're reading a lot into what few details we know about this girl's death.
I bet in the idyllic 1950s -- when men were strong manly men, women were dainty housewives concerned with whether their floor cleaner was a "white tornado", children were seen and not heard and every school child was above average -- there were broken families and domestic tragedies involving children. Both the broken families and tragedies were kept out of sight.
There were plenty of families who stayed together because divorce was difficult, and where children suffered from mental or emotional abuse from one or both parents because they couldn't stand each other.
I don't think keeping families together "because of the children" actually helps children.