^^ I think the same for Tifa goes for all of the FF7:AC characters who make an appearance in KH2. I've looked at Cloud and Cid, and they lack the arm ribbon too, so I'm assuming that Yuffie lacks one as well.
**Someone correct me if I'm wrong
As for other changes, I don't really recall there being any other differences. I haven't watched Advent Children for a while, but if I find anything else that differs from AC Yuffie and KH2 Yuffie I'll post again