I am so sorry for where you find yourself at the moment - not just losing your mum but discovering so much about her that you didn't previously know.
Your mum comes from the the same generation as I do and I think I have some understanding of why she behaved as she did. The sixties was a time of great social change but that didn't mean that there was a sudden revolution for those of us who had been brought up in what had been a pretty conservative society. Before the pill, a pregnancy out of wedlock was a scandal and a mental illness was something so shameful that it was always kept secret.
A few months ago I visited my sister to celebrate her 80th birthday. During one of our more private chats she told me that at one stage in her life she had suffered terrible depression. This was the first I ever knew of it and I was shocked as I would never have guessed. She had never told anyone else in the family. But I couldn't bring myself to tell her that I have also been undergoing treatment for the same condition. Indeed I have never told my children that I currently take antidepressants and have been seeing a psychologist and I know that they would be shocked if they knew.
It sounds as if your mum had a really rough time and maybe she really never intended that you would be exposed to that knowledge, maybe she was trying to protect you in a way that these days might be difficult for you to understand.
I also know that there are things in my life that I will never tell anyone let alone my children because they are so intensely private, personal and painful. My kids don't need to know these things and they will always remain untold and that remains my right to keep those things private.
When you have depression, you get very good at putting up a facade so that no one guesses, that no one knows how miserable you are. Why would I want my children to know that? Especially when I know better than anyone that they can't help me with this and it is a burden they do not need.
I have no doubt that your mum did her very best under the circumstances and perhaps there were many times where your life was impacted by her condition.
But I hope that you can forgive your mum for how she handled things and realise that she wasn't being deceitful, but that she had a right to her privacy and a right to keep her pain hidden from you.