Actually, I don't think overpopulation has much to say to this. Pretty much everywhere on earth, people are having fewer children. Lo and behold, the minute women get the chance to, they have fewer kids. (By the way, the best guarantee of a lower population is women's rights . . . if women have access to birth control and are allowed to use it, they will use it) That's why the population is going to peak at 10 billion in 2050 and then start to drop rather quickly. And the only reason THAT is going to happen is that Africa and the Middle East have a huge generation that is just coming into their childbearing years . .. but no one expects them have have all that many children per couple. Probably between 1 and 3, which is what people are at, or are moving towards, everywhere. The one place where they DO limit how many children people can have, China, is beginning to regret it . . . because they are now below replacement and they have no idea how they are going to care for all those old people with the generations after them being SO much smaller. Oh, and then there's the issue of having too many boys and not enough girls, which will further crimp population but many lead to unrest . . .
Yes, there are too many people . . . but it seems that the problem is, in fact, taking care of itself. Once the current "pig in the python" is through (and that was the result of modern medicine meeting traditional societies . . . people were used to having lots of children, but not used to all of them living) the population will drop, and it will do so due to voluntary choices.
This lady is an outlier by any standards. 20 living children would have made her remarkable in any era, and choosing to have that many makes her unusual today. But our overpopulation problem is not due to people like her, and her 20 kids won't make much of a difference.
I think her decision to have 20 kids is odd . . . but we are allowed to be odd.
PS: I'm rather annoyed with people who are complaining about over population ( a real problem) yet seem unaware of the actual demographics of the situation, let alone the issues raised by too rapid a decline in births. Of course, I'm just as annoyed with those on the right who seem convinced that anyone who suggests that people should have fewer children because of overpopulation is actually suggesting genocide.