Charles Ellicott Commentary Exodus 2:7

"Then said his sister to Pharaoh`s daughter, Shall I go and call thee a nurse of the Hebrew women, that she may nurse the child for thee?" — Exodus 2:7 (ASV)

Then said his sister. —Miriam had waited for the right moment. She had still kept in the background, but had approached within hearing distance. When the princess observed that the baby must be “one of the Hebrews’ children,” Miriam promptly replied, “Shall I not fetch thee then a Hebrew mother to nurse him?” If the child was to be nursed at all—if he was to be brought up—a Hebrew nurse would be the most suitable.

That she may nurse the child for thee. —“For thee.” Miriam discerns the princess's thought, or partly discerns and partly anticipates it, and helps it to take a definite form. She assumes that the child is to be brought up, and for the princess, as her protegé, at any rate, if not something more.