She is both serious and fanciful. Strict and stern, yet kind and lovable. Old and wise and still young and innocent. A witch and a Time Lord.
What was that last one again?
Certainly Mary has a number of traits that could be considered magical and even witch like. But there are other times her crazy world could be explained easier if she were in fact a Time Lord. Both seem as likely as the other to be honest.
Mary as a Witch
Mary has a number of qualities that make her seem more like witch or some sort of magic user.
Indeed a lot of what she does is called magic. It could be that is just what she is calling it to help explain it to the locals.
20th Level Witch Eclectic Tradition
From The Witch
Death Ray or Poison: 5
Magic Wands: 6
Dragon Breath: 8
Rods, Staffs and Spells: 7
To Hit AC 0: 14
Hit Points: 50
AC: 7 (coat equal to leather)
7th level: Speak to Plants and Animals
13th level: Permanent Magic
19th level: Witch’s Blessing
Cantrips: Alarm Ward, Animate Tool, Dancing Lights, Ghost Sound, Object Reading, Warm
First: Comprehend Languages, Everlasting Candle, Fey Sight, Light, Magic Circle Against Evil, Consecration Ritual (Ritual)
Second: Augury, Detect Thoughts, Guard Watch, Mind Obscure, Rite of Remote Seeing, Calling the Quarters (Ritual)
Third: Astral Sense, Dispel Magic, Scry, Spirit of Albion (Avalon), Imbue Witch Ball (Ritual)
Fourth: Analyze Magic, Divine Power, Ethereal Projection, Remove Curse, Drawing Down the Moon (Ritual)
Fifth: Calm Weather, Dream, Greater Command, Seeming
Sixth: Anchoring Rite, Greater Scry, True Seeing, Legend Lore (Ritual)
Seventh: Ball of Sunshine, Greater Arcane Eye, Binding Ritual (Ritual)
Eighth: Astral Projection, Discern Location, Mystic Barrier
Magic Items: Umbrella (works as a Witch's Staff), Bag of Holding (Greater).
Very Experienced Master
From Ghosts of Albion
Life Points 44
Drama Points 10
Contacts (Underground) 3
Contacts (Supernatural) 6
Good Luck 2
Hard to Kill 2
Nerves of Steel
Occult Library (Amazing)
Supernatural Senses (the Sight)
Adversaries (Lots) 5
Metal Problems (Cruel, mild)
Metal Problems (Intolerance, mild)
Obligation (To the family she serves)
Observation 1d10 + 11
Lesser Sensing +19
Armed Mayhem 2
Drive / Ride 2
Knowledge 7 (Science, Mathematics, Astronomy)
Languages 7 (English, Italian, Latin, Greek, French, Animals)
|Dodge / Parry||+2||-||Defense Action|
|Magic||+23||per spell||Usually graphs a horoscope first|
|- Counterspell||+20||Special||Magic defense action; dispels spell|
|- Deflect||+23||Special||Deflects spell 45 degrees|
|- Hold||+22||Special||Magic defense action; delays spell SL turns|
|- Deflect||+16||Special||Magic defense action; returns spell to caster|
These builds assume that Mary is one of the more powerful witches in your game. Of course to deal with children she would not need to be this powerful.