Gaia is properly understood as our mother in that we spring from her/it.
Mother also suggests a loving bond, and I think that is crucial. In industrial society we have objectified our relationship to “the planet.” And we are going insane. We will move toward sanity as we notice how we are nourished by our contact with natural systems, like a walk in the woods. And we will move toward sanity as we care, actively, for aspects of Gaia. As we express our love for our mother, whether by whale watching or by fighting pollution, we strengthen the wholeness of the system of which we are a part.
On the other hand, I find myself loving the old medieval language of masters, mistresses and servants. “Lady Gaia” has a formality and a sense of distance between adults in different stations that “mother” does not.