The Witch's Diary by Rebecca Brae

The higher you fly, the farther you fall. And I'd be surprised if the grubs in the Ascariim deep mine didn't hear my splat.
Hester Wishbone has it made. A recent graduate of Grimoire College, she has a great job as a village hag and is eagerly awaiting the arrival of her familiar. She is also well on the way to earning her Adept Witch designation.
But her perfect life starts to unravel. After an unfortunate incident involving a flammable prosthetic nose, Hester loses her job. Her assigned familiar turns out to be a cockroach. And her magick seems to be well and truly gone.
With time running out on her Adept qualification period, Hester embarks on an epic job search. Her quest takes her to sticky gingerbread houses, dank bogs, and even the dreaded Outerplane (which is a Level 7 Magick Null Zone). Through it all, Hester must figure out what kind of witch she is, if she has no magick.