It becomes clear in the season one finale that instead of a regular shmegular fellow witch, Miss Wardwell is actually Lilith — "the mother of demons, the dawn of doom, Satan's concubine" — and hopes to groom Sabrina to take her place so she can be the "queen of Hell."
Sabrina definitely doesn't strike me as someone who's down to be Satan's concubine — when has she ever followed a rule or let a man (or beast) control her? Also, she's not completely insane. So I don't know why Sabrina is such a great candidate for this role, but I'm going to need to find out soon. This could be some Harry Potter sh*t I might not be ready to relive.