Rachel became a Heroine for two things, first for agreeing to let Leah marry Jacob instead of her without letting Jacob know.

Genesis 29:20. And Jacob served seven years for Rachel and they seemed to him but a few days, because of the love he had for her. 21. And Jacob said to Laban, “Give me my wife, for my days are fulfilled, so I may go in to her.” 22. And Laban gathered together all the men of the place and made a feast. 23. And it was in the evening that he took Leah his daughter and brought her to him, and he went in to her. 24. And Laban gave Zilpah his maid for a handmaid to his daughter Leah. 25. And it happened that in the morning, behold! It was Leah! And he said to Laban, “What is this you have done to me? Did I not serve with you for Rachel? Why then have you tricked me?” 26. And Laban said, “It must not be done this way in our country to give the younger before the firstborn. 27. Fulfill her week and we will give you this one also for the service, which you will serve with me yet another seven years.” 28. And Jacob did so and fulfilled her week, then he gave him Rachel his daughter to wife also.