Genesis 16 gives Hagar a set of firsts that the narrative does not draw attention to. She is the first person in the book to be met by the angel of the Lord. She receives an annunciation, a promise that her descendants will be too many to count, phrased in the same terms used to Abraham. Her son is named before his birth, which happens to only a handful of figures in the whole Bible. And she gives God a name, El Roi, the God who sees me, saying that she has seen the one who sees her. Nobody else in the Hebrew Bible does that.
She is also a slave, pregnant by her mistress's arrangement and running from her mistress's cruelty, and the angel sends her back to it. The text does not resolve the two things it has put side by side.
The second wilderness scene, in Genesis 21, is harsher and shorter. Sent away with bread and a skin of water after Isaac's birth, she puts the boy under a bush when the water is gone and sits at a distance because she cannot watch him die. God hears the boy, not her, and opens her eyes to a well that the text implies was there all along.
Paul, in Galatians 4, turns her into an allegory of slavery and of the covenant at Sinai, set against Sarah as freedom. Twentieth century womanist theology took her back. Delores Williams, writing in 1993, read Hagar as the figure of the enslaved woman who survives in the wilderness with a child and no protector, and made her the central biblical figure for Black women's religious experience in the United States.