She had dreams all yesternight Of her own betrothèd knight; And she in the midnight wood will pray For the weal of her lover that's far away. (27-30)
It would stand to reason that Christabel is a naturally compassionate person if she's concerned about someone she likely hasn't met yet.
Then Christabel stretched forth her hand, And comforted fair Geraldine: O well, bright dame! may you command The service of Sir Leoline; And gladly our stout chivalry Will he send forth and friends withal To guide and guard you safe and free Home to your noble father's hall. (104-111)
Christabel is so warm-hearted that she never even questions Geraldine's story. On a related note, Christabel would make a terrible FBI agent.
O weary lady, Geraldine, I pray you, drink this cordial wine! It is a wine of virtuous powers; My mother made it of wild flowers. (190-193)
Sir Leoline was probably saving that wine for a very special occasion, Christabel.
Sir Leoline, a moment's space, Stood gazing on the damsel's face: And the youthful Lord of Tryermaine Came back upon his heart again. (427-430)
It's that moment in the Hallmark commercials where everyone goes "aww" and grabs a tissue—you know, if Hallmark commercials had witches and stuff.