Because she has no title or any value except what she can do for the Oda. She lacks the status for the Oda family to bring her in like that, but Oda wouldn't trust any of his retainers to be her husband lest they use the opportunity to take her for themselves.
Letting her act independently as long as she proves loyal is the best way to keep her under his leadership.
@Morgan_spurlock
I think she's excited in the novelty of it all. I mean seriously the situation is crazy enough as it is with her advancing historical development and effectively paving the way for modernization (to a limited degree)
But if this works out with the Portuguese missionaries then she international trade and European goods and south east and central Asian goods along with would come to Japanese shores earlier by centuries. This would mean European gunpowder and firearms, rubber from South East Asia, Spices from India and China, possibly even coffee and cacao plants.
As a social studies major, this is the sort of historical what if moments that make me really enjoy this story and other more historical/technically grounded isekais.
@Panino I'm kind of guessing that she has an inkling of Portuguese just enough to get the missionary curious or she uses her future knowledge about the guy's personality and eccentricities.
Oh oh. We might get to meet "yasuke" the only black samurai
Probably not rubber. Rubber tree is native to South America and only smuggled to Britain later, before it was sent to cultivate in India and other colonies. I don't know exact timeline but I think it is too early.
Btw, do you have any historical/technical stories recommended? I read bookworm, daites and youjo senki.