From what I understand, the Goddess's duties during the year involve preparing the Earth to bring forth new life in the early spring, bringing forth the new life in the spring (Obviously with the god's help...but seriously, takes two to baby, so...), nurturing the new life during the summer so that the land is fruitful. In the Autumn, she slows the flow of energy so that the harvest can be successful, and during the winter, she rests and allows the Earth to rest so that when her consort returns from the Underworld, they are prepared to bring forth new life once more.
She's also a guiding force at times, and helps impart wisdom and fruitfulness to any who call on her.
Mind you, i don't really follow the Sabbaths, nor do I observe the "God/Goddess" pairing. So, the only way I know this is from reading the "Wheel of the Year, Living the Magical Life" by Pauline Campanelli with illustrations by Dan Campanelli. I wanted to know why things were associated with certain Sabbaths and seasons, and this book gave me a good idea. So, I can give you basics whereas someone who actually follows those deities can give you details. I do know that some of the Sabbaths are meant to celebrate the Union of the God and Goddess and their life together in the cycle of the year. I also know that some consider the Goddess reborn in the spring with her Consort, so she is Maiden again, to Mother, to Crone.
You say "Witch" like it's a bad thing!