Genesis 16:7

And the Angel of the Lord found her at the fountain of waters in the desert; at the fountain of waters which is in the way to Chagra.

וימצאה מלאך ה, the angel found her in a state of readiness to receive a Divine vision. As a result, he appeared o her. [after all it is not likely that an angel roamed the earth looking for Hagar. Ed.]

על עין המים, she was engaged in prayer. Compare Pessachim 11 where the words of the angel in verse 11 כי שמע ה' אל עניך "for the Lord has heard your affliction" are understood as referring to Hagar's prayer prior to her receiving this vision.

על העין, at a junction of the roads. Whenever there is a juncture of two roads this is described as עינים. The place where these two roads commence is called פתח עינים. In Rabbinic parlance this is known as פרשת דרכים, "a parting of the ways." (Ketuvot 17)

בדרך שור, this is a place known as חגר, as interpreted by Onkelos. This is a town on the order of the land of Israel, or just beyond the border as mentioned in Gittin 2. The Torah informs us by mentioning this detail that it had been Hagar's intention to emigrate from the land of Israel (Canaan).

וימצאה על עין המים, after the Torah wrote the words על עין המים, it goes on to explain this term, i.e. על העין, "next to the fountain she had discovered." על העין, the definite article ה means that this well on the route to Shur was known. She was therefore on the way back to Egypt, the land from which she had originated.