In traditional Wicca, and also some other religions, the Goddess is often viewed as a triune of the Maiden, the Mother, and the Crone, or as the Maiden, Warrior, Mother, and Crone. There are also the subdivisions of "Bright" versus "Dark", and these classify certain attributes such as life-giving versus death-dealing, gentleness vs wrath, soft-spoken vs aggressive. I do not connote brightness with good, nor darkness with evil, as such is far too simplistic.
I see Xena as a super-mortal being:
She is a warrior of legend, whose beginnings have been shrouded in the mists of time. She is a woman possessing powers far beyond those of ordinary mortals. She is said to have the "strength of ten men" [Altared States]. She has died and lived again [The Quest]. She has battled Titans and cyclopses [Titans], and has fought against the great centaur armies [Hooves and Harlots]. There is no mortal like her.
Xena has undertaken the mythical/traditional Journey of the Divine into the Underworld/Death:
We are familiar with the Descent of Inanna into the Underworld, where, as the great Goddess passes each of the gates to hell, she has to give up an item of her power. She experiances death, is brought back to life, and as she rises from the Underworld, gains back her power and more.
We have seen Xena also undertake a similar journey of death, revelation/growth, and subsequent resurrection [Destiny/The Quest]. Xena dies only by an act of her own will - she gives up on life. Her death is a learning experiance - inner secrets are revealed to her. Through death she finally accepts her love for Gabrielle, and she acknowledges her destiny. Once this is done, she is ready to live again, and rises from the grave in all her glory.
Xena has known both Darkness and the Light:
She is the Dark Mother, the bringer of death, the Destroyer. Hers is the power of death; her kiss, the cold of steel. But Death is not neccessarily bad or evil, for this power can be a double-edged sword, symbolised by the one she carries. The Sword of Xena may burn innocent villages to the ground, or it may just as easily slay an evil warlord or a murdering giant [A Day In The Life] and in so doing save many other lives.
She is also the Maiden Bright; she who lives for the joy of the moment, who laughs in the face of adversity. She touches other lives with her light, including Gabrielle's. She administers healing. She is a force for positive change in the world, and is herself in a constant state of change and growth.
Xena's Touch can heal or kill [Royal Couple of Thieves], and her Sword may slay or save. Her Voice may order the taking of a village, or sing a soul to peace, or outdo the Sirens.
The Darkness is the strength without which the Light would not be, for the Darkness and the Light are one in Her.