Over the years, Ellen Creighton has given birth to no less than twelve children. Inevitably, this has taken a toll on her physical appearance. Back in the 1830s, when she married Matthew, she was a very pretty girl. But such prettiness is short-lived for country women at this time. Before long, their good looks are adversely affected by the strain of regular childbirths and the immense toil that raising children requires.
That's what's happened to Ellen. If she's concerned about it, though, she's not showing it. This is because Ellen's value system, steeped as it is in Calvinism, doesn't permit her to display the vanity of regret for a fading beauty. She could get upset over the loss of her looks, but, according to the values of her religion, that would be allowing her vanity to get the better of her.
In any case, the loss of Ellen's beauty is of little importance in the overall scheme of things. This is a woman who's lived through sickness, poverty, and danger for over thirty years. And yet, despite all that, she's survived and has raised a large family. It may be a pity that Ellen has lost her looks during this time, but her family matters so much more to her.