Yeah, Jill's understanding of the world beyond Rodoria is quite rudimentary. She's familiar with a handful of names here and there, could place them roughly accurately on a map, but otherwise knows only some horror stories from the Catolohne, whose culture she finds revolting (unsurprisingly, given she's a relatively emancipated woman). Contrasting Jill and Aemoten this way is kind of funny though, given her prejudices of him while he is far more liberal and accepting than she is. Point in case, she's even tolerant towards arranged marriages to an extent, given that the practice isn't horribly uncommon in higher circles and even her own sister was pressured into a convenient, rather than a passionate marriage. She's been raised to see lineage as an important value, and arranged marriage is an efficient method of ensuring the strength, purity and simply survival of these. A necessary evil, so to speak.
Admittedly, though, I'm not 100% in the know of everything going on in the IC. Is there something particularly scandalous about this marriage between Zerul and Pelgaid that I'm not aware of? The description given by you two seems to paint the affair as something a little more extreme than what I'm imagining on a whim.