According to Exodus, Moses’ sister who watched over him in the Nile was Miriam.
Exodus 2 tells how Moses’ mother placed him in a papyrus basket among the reeds along the Nile to protect him from Pharaoh’s order concerning Hebrew boys. His sister stood at a distance to see what would happen. When Pharaoh’s daughter found the child, the girl offered to find a Hebrew nurse, allowing Moses’ own mother to care for him.
The chapter does not name the sister at that moment, but later biblical passages identify Moses’ sister as Miriam. She becomes a prophet and leader alongside Moses and Aaron, and Exodus 15 portrays her leading the women with tambourines and dancing after the crossing of the sea.
Miriam is sometimes confused with Pharaoh’s daughter, who discovered Moses, or with Zipporah, Moses’ wife. Those are separate figures. Miriam’s role in the basket episode is established by the later identification of Moses’ sister.