The angel asked Hagar questions that helped her speak openly to God. When she did, God told her to return and submit to Sarai (16:9). He also promised that her son would have many descendants, so many that they could not be counted.
The angel of the Lord did not call Hagar Abram’s wife. Instead, he called her Sarai’s servant. Hagar would bear Abram’s child, but Ishmael was not part of God’s covenant with Abram.