How would the relationships between the princesses be: Snow White and Tiana?

Well, she'd obviously fustrate her, maybe even sometimes irritate; but I don't think they'd hate eachother; Snow, in a way at least would probably admire her; and ((as in a fanfic I read) I think Tiana could be a good role model/mother figure

They might not be as close as Snow/Punz are, but I think they'd get along well. Tiana might be reminded of Charlotte, with how romantic and idealistic Snow is, and Tiana would find her motherly bossiness charming and relatable. Snow would look up to Tiana for how she believes in working hard and honoring her dad, though find her a bit pessimistic at times. they would bond over cooking and Snow would try to get Tiana to take time for herself and have fun more. Tiana would feel protective of her like a big sister, though find her domineering and optimism a bit trying at times.

So they'd be good friends, I think, overall, but not always be that close due to Tiana being Mehr mature and grounded.