It is Miriam  who was always the speaker of the three siblings. 

Miriam, who, according to the Talmud, was also called Puah because of the sounds she made to soothe women in childbirth as their babies emerged into the world. Miriam, who used her words to stand up to her father when he separated from his wife, insisting that a chance at life, however small, was better than no chance at all. Miriam who quickly figured out what words would ensure that Pharaoh's daughter would adopt Moshe, creating the path to redemption.