Molly is the real Good Witch
The previous good witch gave her powers to Angel knowing she would abuse them to create, inspire, and empower Molly as her nemesis.
Eventually, a Wicked Witch will be introduced
Ironically said character will be a Good Counterpart
To Angel and use her Black Magic to Help others. Bonus points if she's named Lilith
- Adding to this, the mortality of Good Witch could play apart into this. Since the Wicked Witch would naturally be opposed to her, this time around (since Angel's for lack of a better term, a Sociopath), the wicked witch's powers was passed onto someone who is basically a Messianic Archetype.