If Reksai spoke she would just be a female nocturne

And lose all the cool aspects of her

She is a metroidesque monster

Ridley is a monster and that's all. Just because other pirates in that series speak doesn't mean he needs to.

Reksai could honestly just be the most hostile and animalistic void monster we have seen yet. Why must we just make her like everyone else and give her some boring voice over like "kill all the things" which is most of the void anyway even kha