The irony is that by setting him free out of her love for her, she is also setting herself up for loss because when he goes to college, he meets another girl, a town girl, and he forgets his backward country girl friend. She sets him free, and it results in him growing away from her. I think this episode shows well how Mary is mature beyond her years - love for her is already not "wanting" the other person, but to go along with what is best for that person. And in a way she is already aware that this may cause him to grow away from her as well because just as his adoptive parents, Mary symbolizes the peasant background that he wants to get out of.
The irony is that by setting him free out of her love for her, she is also setting herself up for loss because when he goes to college, he meets another girl, a town girl, and he forgets his backward country girl friend. She sets him free, and it results in him growing away from her.
I think this episode shows well how Mary is mature beyond her years - love for her is already not "wanting" the other person, but to go along with what is best for that person. And in a way she is already aware that this may cause him to grow away from her as well because just as his adoptive parents, Mary symbolizes the peasant background that he wants to get out of.