In many ways, the fabulous floozy and boozy mom is the book's most realistic character. Things are messy and never romanticized with her. Melena challenges conventional ideas of marriage, fidelity, and parenthood. Though she's far from being an ideal mom, her maternal role is a crucial one in Elphaba's life.
"Even for a short time," said Elphaba, "we had a mother. Giddy, alcoholic, imaginative, uncertain, desperate, brave, stubborn, supportive, woman. We had her. Melena." (188.8.131.52)
Even as a child, Elphaba recognizes the complexities of her mother, and she often seems to be searching for something else in her:
Elphaba cocked her head to one side as if listening for some part of her mother not intoxicated with leaves and wine. (1.5.10)
As a young Elphaba recognized, the real Melena exists underneath all the exterior trappings of her looks, her substance abuse, her dissatisfaction with her life in Munchkinland. Melena is always seeking something deeper and more meaningful in life: it's why she fled her wealthy childhood home of Colwen Grounds and it's why her spiritual awakening/love affair with Turtle Heart is so significant.
In her search for meaning, Melena shares vital parallels with her daughter. Mother and daughter also share other important experiences and traits: their dreams of other worlds, their rebellious natures, their anti-Hallmark experiences with motherhood, their experiences with love. Elphaba may focus her attention on Frex, but she mirrors her mother's life in some key ways. And near the end of her life, she starts paying more attention to those connections and to the mystery of who her mother actually was.