In the 1950's there was little tolerance for the mentally ill. They were either locked up in Asylums, given shock therapy or just ignored.
I could see that as a valid reason for not being able to get much appropriate help, if someone had tried to. I can't really accept it as a valid reason for not trying. I'm not sure from what you say whether your mother did try. Perhaps she did.
I'm from a later generation, when there were therapists, feminism, and a multitude of self help books. Did my mother try a single thing? Not that I'm aware of, and I'm pretty confident that means no, not a thing.
In a situation like this, I would always hesitate to attribute things to how society was in the past, because there have always been things in society that could help people. In the past, religion and talking to priests would have applied to more people than today. Doctors had more time to talk, and in general they knew their patients. Self help books of various kinds, and stress management/anxiety techniques, have been around since the early 1900s.
To me, the point is not what was assumed/expected about trying to get help, but whether they actually tried.
After all, I have had to go to therapy when feeling hopeless and despairing. I've had to look for and find a therapist while feeling like that. Why shouldn't the person who caused so much of my childhood misery have been expected to do the sane?
Your point about shock therapy sums it up for me... it was me who ended up having electro-convulsive therapy for my psychological problems, not my mother. Because I was actually trying to do something about my condition, unlike her.