God doesn’t “create” Barbelo per se; instead, she comes from him by some indirect means. For example, in some Gnostic texts, God’s inexhaustible profusion of thought overflows, and a new being, Barbelo, emerges from that intellectual flood. Elsewhere, it’s said that Barbelo arose when God stared down into the primal waters and saw his luminous reflection, which then became a new being.
We don’t know what the name “Barbelo” means, but it might be related to the Coptic verb berber, “to overflow” or “to boil over.” That connection would be fitting in light of Barbelo having been born from the overflowing thought of God in some Gnostic scriptures.
In the Secret Book of John and other classic Gnostic texts, Barbelo is portrayed as the mother of Christ (who, in much early Christian literature including Gnostic literature, is thought of as a divine being who existed long before he was ever incarnated in human flesh through Mary). God the Father, Barbelo the Mother, and Christ the Son form a three-member divine family. The Gnostics thought of this as the divine model of which all earthly families are an imperfect, corrupted reflection.
If that heavenly family sounds a lot like the Trinity of the Father, Son, and Holy Spirit, that’s probably no coincidence.
The word for “spirit” in Hebrew and other Semitic languages is feminine, so to the ears of people who spoke those languages, the name “Holy Spirit” would have almost automatically connoted a feminine being. This seems to be a conception that was actively cultivated in at least some early Christian circles. For example, the Jewish Christian Gospel of the Hebrews has Jesus refer to the Holy Spirit as his mother.
The same view is attested in Gnostic literature, too. In the words of the Valentinian Gnostic Gospel of Philip, “Some said Mary became pregnant by the Holy Spirit. They are wrong and do not know what they are saying. When did a woman ever get pregnant by a woman?”
To be sure, the idea that Barbelo, the divine mother of Christ, is identical to the Holy Spirit is seldom explicitly asserted in Gnostic texts. We should therefore be careful about categorically claiming that this was a view held by all or even most Gnostics. But the extant Gnostic texts certainly seem to assume such a view in their mentions of Barbelo, such that we can indeed tentatively ascribe that view to most if not all of the Gnostics.
 Brakke, David. 2010. The Gnostics: Myth, Ritual, and Diversity in Early Christianity. Harvard University Press. p. 53-54.
 Lewis, Nicola Denzey. 2013. Introduction to “Gnosticism:” Ancient Voices, Christian Worlds. Oxford University Press. p. 154-156.
 Ibid. p. 155.
 Turner, John D., and Marvin Meyer. 2008. “The Secret Book of John.” In The Nag Hammadi Scriptures. Edited by Marvin Meyer. HarperOne. p. 103-132.
 See, for example, the first chapter of the Gospel of John or any of the many Gnostic texts that describe how Heaven was first populated before the creation of the world.
 Brakke, David. 2010. The Gnostics: Myth, Ritual, and Diversity in Early Christianity. Harvard University Press. p. 55.
 Scopello, Madeleine, and Marvin Meyer. 2008. “The Gospel of Philip.” In The Nag Hammadi Scriptures. Edited by Marvin Meyer. HarperOne. p. 164, footnote 16.
 Ibid. p. 164.