What do you think is the real reason that Eugene’s mother turns Elena away?

Elena develops a serious crush on Eugene. He is a tall, blonde, blue-eyed boy with glasses who just moved into the neighborhood. Eugene's family originally hails from Georgia, and his Southern background and upbringing merely add to the fascination for the increasingly smitten Elena. Soon, Elena and Eugene are spending a lot of time together. But what Elena wants most of all is to go visit Eugene's family at their home. She has started reading Gone with the Wind, and she fantasizes about what kind of life Eugene's family leads.
Elena soon gets her wish. But on the day she is due to visit Eugene's home for study, the nation is plunged into tragic grief by the assassination of President Kennedy. Nevertheless, Elena is so excited by her forthcoming visit that not even a great national tragedy can prevent her from going. She heads off to what she thinks will be Tara, Scarlet O'Hara's plantation in Gone with the Wind.
But when she shows up at the house, Elena is utterly humiliated as well as disabused of her romantic preconceptions. Eugene's mom answers the door and tells Elena that he is a smart boy and does not need any help with his studying. In any case, as they will not be living in the neighborhood much longer, there is no point in getting close to people.
These are the reasons that Eugene's mom gives for not allowing Elena into the house. However, the real reason is likely that she is prejudiced against Elena for being Puerto Rican. She also appears to harbor some social snobbery against Elena and her family for living in the "ugly gray prison" of El Building.