We just saw their first interaction on manga, and the fact Yatsude said "Fuji being Fuji", they already knew each other, but still it's their first interaction, the character development is not there yet.
I think I know which pictures and lines from the manga would make you think Fuji's ship is with Yatsude, but also that you're putting too much weight into those compared to Fuji and her onee-san. I believe Yatsude's shown more interest in finding out if Yokoe and Kei-chan are a couple than in any romance for herself.
I'd rather let each reader decide for themselves though, since I'm planning on translating all those extras after volume 3, too.