The balance to this game is so weird, and its compounded by how different the power curve is for each character. In the end, I guess it shakes out as Soma > Alucard > Charlotte > Shanoa > Jonathan, but if you start everybody from scratch and play them for the same amount of time, there's pretty significant stretches of time where Shanoa is the most powerful, Charlotte is queen for a while, and Alucard trumps Soma pretty handily until you get some majorly lucky drops from Hard mode Dracula. Poor Jonathan, though
Shanoa's spell glyphs all come from Aliorumnas (the glowing, floating witches), except for Nitesco, which comes from the Nova Skeletons (green ones). You start running into Aliorumnas on level 2, but the ones there only have her Ice glyph. The ones in later stages (4, 5, and 6, I think) have her lightning glyph, and the Nova Skeletons are in stages 5 and 6.
Her weapon glyphs (Lapiste, a stone fist attack, and Pneuma, a wind attack) are only found in boss chests; I'm not sure if it's only specific bosses or not (but I think Pneuma might only be found from stages 4-6). You don't need to play on Hard to get any of her glyphs.
Shanoa kind of gets the shaft in terms of the number of weapons and spells she gets, but on the positive side, pretty much all of them are useful. Pneuma and Fulgur (lightning glyph) are her best ones, though.