It's interesting to note the romantic Claudium in Book 2 novelization here and the revelation that Claudia really liked Callum enough to kiss him willingly - if not for her plans.
There's a mutual attraction, sure, but Claudia wasn't interested enough to understand Callum's side of the story. And Callum was an awkward mess around Claudia to express himself more.
And despite her desire to win his trust, Claudia never dared to use his feelings as her advantage. She even gave Ezran a powdered drink (lemonade) for Callum to drink once he wakes up from using Dark Magic (tho there's no mention in the book that Ez gave it to Callum)
Unfortunately, Callum took the hard blow. He trusted Claudia, and as much as he hates to admit it, maybe loved her.
But was it really love?
Enter platonic-but-not-really Rayllum who have been bickering and pissing each other off in a friendly-but-not-really manner since Book 1. They don't know anything about each other than their common mission. Callum don't know anything personal about Rayla - her family/friends/home - as much as he knows about Claudia, but he has revered her as heroic and brave, and even considered himself lucky to be her friend.
Anyway, I can't wait to get on hold of Book 3 Sun and read how these two dorks found each other and Claudia falling into corruption