When I researched my birth family my natural mother had died. I only made contact because I had two older half sisters. As I was two when I was taken by the authorities I thought they might remember that disappearing child. They had absolutely no idea that I existed. They never saw me or heard about me, so it was a huge shock for them. I still don't know how she gave birth and had me looked after without them suspecting, but she did.
I felt no connection with my half sisters or they with me. I think I must take after my father, but I have no way of finding out who he was. Her husband was away in the war, and I was adopted because he refused to reconcile with her unless I went. Not that I was with her anyway, but my adoption made it permanent. I seem to have my natural mother's digestive system as she died of complications with that. I also worked in Accounts as she did.
Seriously watch what you eat, is all that I can say to the digestive problems. And I do mean seriously. It does help.
So your mother had a child while her husband was away in The War. Her and thousands like her. Some of their husbands were a bit more kind. Some husbands went away even though they didn't need to.
Some older children were evacuated, so wouldn't have known anyway. But she doesn't sound like a particularly bad mother to me.
You and I also have something else in common. We were both married to Service Men who were away from home on occasions, mine for longer periods than yours. Which is how I came to leave my children while I went next door for a cup of coffee and a chat. Two years at sea was very ordinary in those days, and not much fun to be left alone with two small children and not a lot of money for as long as that.
I have never given my reasons before because I didn't think I needed to make excuses. I still don't. I mention it now only in passing.