The Leia thing was stupid for two reasons - one, she was never meant to be Luke’s sister and Luke was obviously attracted to her in the preceding two films (with deleted scenes clearly showing an attraction from Leia’s side as well - not ‘canon’ but certainly indicative of the writers’ intent).

Secondly she was a prisoner on Bespin while Yoda made the “there is another” declaration in the first place, so she could not possibly have been the other hope - sister or no. At best you’d have to argue that Yoda, who previously couldn’t ‘see her fate’, suddenly sensed through the Force (as Luke was taking off) that Leia would survive the Bespin fiasco but somehow he couldn’t see that Luke would make it as well. Or something…

Personally I think Boba Fett should’ve been the ‘other hope’…