What does Exodus 2:4 mean?

Moses' sister is introduced in this verse. She was clearly mature enough to speak with Pharaoh's daughter (Exodus 2:7). We later discover this sister is Miriam, a woman who plays an important part in the history of Israel and the exodus (Exodus 15:20; Numbers 26:59). Even when she was a child, her courage was evident. Her efforts helped to save Moses' life and keep their mother involved in his young life.

Miriam is next mentioned in Exodus 15:20–21 where she leads the women in dancing and singing with tambourines. She later opposes Moses' leadership and briefly experiences leprosy (Numbers 12; Deuteronomy 24:9). She would much later die and be buried during the wilderness journey in the wilderness of Zin at Kadesh (Numbers 20:1). Micah 6:4 remembers Miriam as being among those sent by God to bring up God's people and redeem them from the house of slavery. Without Miriam, the early life of Moses would have been much different. Even in her old age, likely in her 90s, she rejoiced at the miracle at the Red Sea and led others in worship of the Lord.