There's the episode where Van, Fiona and Thomas are guarding Emperor Rudolf during his vacation, and Thomas works with Marianne to confess his love to Fiona. When he finally musters up the courage to declare his love for her... he accidentally confesses to Zeke. Zeke responds rather positively.
Fiona was quite a bit of a Cloud Cuckoo Lander, but there was one time where the group had to somehow sneak their Zoids by some guards without suspicion. Their strategy? Have Moonbay and Fiona pretend they're off to Moonbay's wedding. The only thing Fiona says throughout the entire exchange between the guards is "My sister's getting married today," with varying degrees of emotion. Amazingly enough, it all makes sense in context.
Fiona's 'rescue' of Van and Moonbay who are tied to the Liger's leg:
Fiona: (Waltzes past the gang) "Van, Moonbay, I'm here to untie you!" (Immediately gets grabbed).
Moonbay: "She's unbelievable."
Irvine: "What was she thinking?" (Having used the distraction to get past the gang himself).