Numbers 12:2 New English Translation

²They^[a] said, “Has the Lord spoken only^[b] through Moses? Has he not also spoken through us?”^[c] And the Lord heard it.^[d]

Numbers 12:2 tn Now the text changes to use a plural form of the verb. The indication is that Miriam criticized the marriage, and then the two of them raised questions about his sole leadership of the nation.
Numbers 12:2 tn The use of both רַק and אַךְ (raq and ʾakh) underscore the point that the issue is Moses’ uniqueness.
Numbers 12:2 sn The questions are rhetorical. They are affirming that God does not only speak through Moses, but also speaks through them. They see themselves as equal with Moses. The question that was asked of the earlier presumptuous Moses—“Who made you a ruler over us?”—could also be asked of them. God had not placed them as equals with Moses. The passage is relevant for today when so many clamor for equal authority and leadership with those whom God has legitimately called.
Numbers 12:2 sn The statement is striking. Obviously the Lord knows all things. But the statement of the obvious here is meant to indicate that the Lord was about to do something about this.

New English Translation (NET)