Yeah! Found it.
All right, I'll sum up what she tells you and more:
There are twelve schools of magic in the game, most of which come in opposing pairs. There's Light and Shadow magics, which are naturally opposed given their nature. The Arcane (tarot cards) and Rune (symbol) magics are an opposed pair. The Realm magic of the Magic Kingdom and the Mystic magic of Facinituru are an opposed pair. Mind magic opposes Evil magic. Time magic and Space magic oppose one another. And I guess by process of elimination Mirage and Life magic oppose one another.
Only one character in the game will learn any Evil, Time, Space, Mirage, or Life magic, so we'll cover those when we meet those characters.
Humans and Mystics can buy spells from certain vendors -- like the one in the screenshot above, for Rune magic -- but can't know spells from two opposite schools at the same time. Furthermore, each school has several spells that aren't for sale. You have to develop those yourself, and to develop spells in a given school, you must have the "Gift" for that school.
Realm magic and Mystic magic automatically grant their gifts to people born in the Magic Kingdom and to the Mystic race, respectively. Eliminating those two plus the five single-character schools listed above, and that leaves Arcane, Rune, Light, Shadow, and Mind magics.
Characters who collect all four runes or all four tarot cards receive the gift for Rune or Arcane magic, respectively. That only covers characters who are present for all four collectibles for each one -- so in this game, only Emelia, Annie, and Liza can have the gift for Rune magic, since they were the only ones to collect the Freedom Rune.
The gift for Mind magic is distributed in the region called Kyo. Light and Shadow magic gifts can be attained in Luminous.
Anyway, this person tells us where to find the four runes needed to acquire the gift:
We head to Shrike.
There's a tomb on the bottom-left corner of the map that looks promising.
Roufas joins the party! He's not too shabby with swords, but excels with guns and magic. He starts with the gift of Mind magic, and a couple spells from that school.
We leave Shrike.
Rouge joins the party! He's a dedicated magician, as you may have guessed, but he's still better with a sword than Annie. And given how the game intrinsically links skill with magic and skill with guns, he's not a bad shot either. He starts with several Realm spells, and being from the Magic Kingdom, has the gift to develop more.
Luminous, as you may have deduced from the name, is the home of Light and Shadow magics.
The gift for Light magic is gained by completing a short maze.
There are no monsters, but you have to open the way forward by shining the beam of light on these wall symbols.
This means you can get this gift in about two minutes if you know the puzzle solutions.
Flip mirrors, move prisms...
There are seven scenarios. You'll be doing some sidequests in just about all of them.
In this puzzle, the beams of light pass through colored barriers that change their hue. Shining different colors on the door here results in different effects (including a couple monster fights, the only ones in the Labyrinth).
Only one worth worrying about is purple, though. Sanctuary Stones are like Tents from Final Fantasy, restoring your party to full. They're rare, though -- you'll only get one or two per scenario, and they don't transfer between scenarios.
White light opens the door, and we're done.
Everyone present has the gift for Light magic now.