(updated June 1, 2023)Where did Leah learn about God? Perhaps from Jacob's story of running for his life from Esau and meeting God at Bethel? Genesis 29:31,32. "When God saw that Leah was unloved..." God sees! He recognizes when we are overlooked, unloved. And there is a blessing in that! "...He enabled her to conceive..." Leah then acknowledged God in that blessing, in the names of her kids. How could Jacob ignore that? Every time he called one Leah's boys he had a reminder that God was with them. She may have been unloved, but she was still an influence in Jacob's life! An influence he couldn't ignore and I believe he acknowledged in Genesis 35:3
(updated July 1, 2023)
I just realized today that in Genesis 49, Jacob (in Egypt) asked to be buried with his fathers and Leah - not with Rachel. Rachel did not get buried with the rest of the family and Jacob specifically calls that out here, at his death.