Having been raised by parents who married young and never fully martured emotionally, I must say your opinion is very judgmental and short-sighted.
It is hell to grow up with an immature parent who lashes out and neglects essentials because they simply do not know any better. I left home at 17 and never went back, and I'm a female. I purposely did not have a child until my late 30s, when I had partially gotten over what happened to me and my siblings (it will never be fully over), but it was only by the grace of God and the availability of birth control that I wasn't in her place, faced with the prospect of taking my family's hurts out on an innocent child.
A baby truly is not a football. There are lots of childless couples who would love to adopt a child from an immature parent and provide what she could not provide: a stable, two-parent home. Rant all you want about getting pregnant out of wedlock, but once it happened and the boy dumped her also, a decision had to be made.
She was not thinking only of herself; but rather she was doing the best thing for the child after the father of the child proved unwilling to step up and she honestly recognized that she was unprepared to accept the enormous responsibility of raising a child as a single mother.
There are single unmarried women who adopt children.
I don't think it's a good idea. A child needs a mother and father and a stable, loving household.