Granmaretto I think you'll find many families cant feed their babies ,even 56 years ago .Poverty grinds women down.They were living in bad housing she had two children to care for and a job ,she couldn't cope with a third.
Nowadays of course she'd be blamed for not using a reliable contraceptive but for the majority of women back then it wasn't available mainly because their husbands didn't want to use contraception.
My mothers generation had a baby every year or two ,there were families of 8 .10 .12 and 14 children in my street in Glasgow ..and no they weren't all catholic families .Poverty was normal ,the father in that case was in the army so he ddn't have to deal with the consequences ,maybe she felt it was the only choice she had