She and Evelyn (see below) are the only two cast members who don't have profiles with Tarot card arcana on the official website.
When upright, it represents mystery and spiritual insight, but when reversed, represents secrets. Geladura knows a lot about Evelyn, due to being the Fairy Queen. Morgan also notes that Geladura has become less helpful than in the past, especially when she doesn't talk to Tara or Madison due to being unsure of whether to trust them.
And no, this is not because she's hands-down the most evil member of the cast. The reversed Devil represents freedom, which would refer to Evelyn's desire to escape Eysenfeld and see the world outside. The upright Devil represents being constrained by negative forces, which refers to Evelyn enslaving the town using Glamour and using them as human sacrifices.
And not because she dies, but that does have something to do with it.
The card represents change and new beginnings. This can refer to Madison wanting to quit Taranormal to get her life back on track, which she does in the good ending. In the bad ending in which Geladura dies, it can also represent Madison becoming Fairy Queen for good, a change that forces her to give up her old life and results in her being essentially dead as far as most people are concerned.
It seems strange that there are four possible dialogue choices for the pre-climax conversation between Morgan and Madison (only two or three of which are available at one time), but the two available if you make the wrong combination of choices give you the exact same ending- the one in which Geladura dies and Abigail and Madison disappear. Let's review each of them.
"You're right." means that Morgan agrees with Madison that no one has to die, and thus achieves the Golden Ending in which no one besides Evelyn/the Moonsick One dies (save for the forest spirit becoming the new ancestral tree).
"I'll make it up to you," involves Morgan deciding that she's to blame for everything Madison and Tara suffered after coming to Eysenfeld, and sacrificing herself to atone for it. Morgan dies, but Madison and Tara, along with Abigail, survive and go home.
That just leaves "One way or another, it ends tonight" and "I'll keep Tara safe." The former would show Tara's determination to defeat Evelyn at any cost, which, unfortunately, would lead Geladura to give the last of her power to defeat Evelyn. "I'll keep Tara safe," would likely correspond to how in the ending in which Morgan becomes Fairy Queen; Morgan refuses to allow Tara to take her place as Fairy Queen, and how she chooses to take Madison's place so Tara won't lose her best friend.
As the artbook points out, Geladura has a winter-themed dress(blue, white and seemingly made out of ice), Madison's Fairy Queen dress is spring-themed(mostly green, has living flowers) and Morgan's Fairy Queen dress from the aforementioned unused ending is autumn-themed (red and has autumn leaves). It thus stands to reason that given Tara's energetic personality, she'd have a summer-themed dress, probably a golden-colored one that evokes the sun.