The second mistake is to base her "scientific" arguments on studies of children who were born in the seventies. Her whole point is that women are increasingly likely to have children out of wedlock - as the original poster said, this means that different kinds of women are making this choice.
So if well-educated, well-off women decide that they would rather have a child in their fertile years and not commit to a legal instrument, you can't expect the consequences of this choice to be the same as those of having a child as a teen mother.
The last thing, is that no research can say that having children out of wedlock is bad for the children, compared to that same woman in a marriage with the children's father. The fact is that you can compare similar children in different situations, but when women don't marry the child's father, there is a reason for that.
Sure, unprotected casual sex leading to an unwanted pregnancy is not a recipe for success. But planned parenthood out of wedlock is something still untested.