Or HaChaim on Numbers 12:1/אור החיים על במדבר י״ב:א׳

1 ותדבר מרים במשה, Miriam uttered criticism of Moses, etc. It is possible that Miriam and Aaron spoke in Moses' presence. Logic would dictate that this was indeed the case. Had they only been talking amongst each other, what difference would it have made to Moses? We must assume therefore that they said what they did as a rebuke to Moses. I believe Sifri confirms my opinion as the author quotes the words: וישמע ה׳ והאיש משה as belonging together, i.e. Moses too heard what Miriam said.