It’s true to that Chani become a character of suspicion and doubt instead of a supporter of Paul. But I don’t think it was a simple we can’t make the woman character look weak kind of decision but more like a comment that Frank Herbert made. He would like to have the character of Paul as a warning for Mesiah figures. The reason he wrote the second book that he felt he was failed to make it felt like a warning and everybody was on board with the messiah figure :). So I think that is why I think they made Channi as she is in the movies. And it is just basically free source of drama so I think it was difficult to resist I don’t know :)