David Johnston wrote:

Why is Ayeka calling Ranma "sama"?  Ranma doesn't outrank
Ayeka.  "fiance", not "fiancee"

I think she is being polite since she does view Ranma as an equal in
terms of her blood.  Remember according to the blood scan (or something
close to that) in a previous chapters Ranma is part of the Jurai Royal
family. ^_^