Both the women you mention - the one sleeping around and the one buying a kid - are part of the problem. But the one buying the sperm for her kid is worse, because she shouldn't be a mother. Period.
Let her get a dog. That's something she can't screw up much, and if she does, it doesn't matter.
But who are you to judge whether she would be a good mother? Do you not agree that there are women who are married who should not have had children? Do you think that b!tch in Texas who murdered her children was a better mother because she was married?