"Witch" is not a good equivalent to 'wizard', because the connotations are very different. We associate the word 'wizard' with cleverness, and associate 'witch' with (female) ugliness and malevolence. The word 'witch' is loaded with centuries of fear, suspicion and downright misogyny. "Sorceress" and "enchantress" are rather more positive, but they are still fairly sexist. In this post-feminist world, I wonder if it's time to reclaim the word 'wizard' and make it non-gender specific? Compared with other languages, English has very little in the way of gender. A teacher, a doctor, a friend, a neighbour, a cousin.... all of these can be either a woman or a man, so why not a wizard? Or, while we're waiting for that to happen, you could try 'wizardess'. It isn't a standard term, but it did get a few hundred thousand hits when I googled it.

witch, hag, sorceress