Quellian-dyrae, thanks for a very prompt, thorough, and positive PEACH. I will commence the re-evaluation based on your suggestions.
Edit: I made a few minor changes, mostly along the lines you suggested. The Guardian Angel's charisma bonus now helps a few of her abilities (and forms the limit for the magic path's capstone). My changes to the stealth path actually seem to have made it weaker, however. Would just increasing the amount of sneak attack (3d6, 6d6, and 9d6, perhaps) put it on par with the others?
Edit edit: I also remembered that the Guardian Angel originally had all bad saves. Changed it so she has all good saves when adjacent to a bonded ally, and all bad saves if not. Also added to the skill list.