Aquarius doesn’t know how to “do” relationships, so who better than Libra, the expert on partnerships, to guide him? The sign of the scales is ruled by Venus, goddess of love. She knows how to navigate the rocky territory of coupledom, using charm, compromise and all manner of secret techniques.
Aquarius is ruled by Uranus. This outer planet is more comfortable at Star Trek conventions than blind dates sipping on mochas. Uranus is all ideas. Libra can connect to him on the mental plane without losing her human touch. Both are air signs, expressing themselves best in the social and intellectual realms. Libra may not be a space alien like Aquarius, but she can tune into his wavelength enough to decode his transmissions.
Why not Gemini women? Although Gemini is also an air sign, it is ruled by Mercury, planet of communication. Uranus is a “higher octave” of the messenger planet. Put together two thinkers and you’ll have some good discussions, but not much incentive to make the connection physical. Some goddess energy is required to take Aquarius out of the clouds and into the bedroom.