Sforno on Genesis 38:14/ספורנו על בראשית ל״ח:י״ד

1בפתח עינים, at the beginning of two major roads. Such a highway is known as עינים, as we know from Genesis 16,7 על העין בדרך שור, “by the road leading to Shur.”

2אשר על דרך תמנתה, so that Yehudah could not avoid meeting her when he would return from Timnatah.

3כי ראתה כי גדל שלה, she thought that when Yehudah would see her without widow’s garments he would ask her why she had shed those garments. She would answer him that the time had come for Shelah to marry her. He himself had suggested that she live as a widow only until Shelah would grow up. In the meantime he had already matured.