What is the significance of the expression on Dona Tina's face at the end of Chapter III?

Yesenia knows that Dona Tina will not have dealt well with the news of Luismi's arrest, which is why she had instructed her niece Vanessa not to answer the door in her absence. When Yesenia arrives home, she is horrified to find that Vanessa has sneaked off to see her boyfriend, leaving Dona Tina alone. The Guera Sisters have visited in the interim, delivering all kinds of details to Dona Tina about Luismi's arrest and alleged crimes. The moment Yesenia enters her grandmother's room, she sees Dona Tina's furious face and she knows right away that she cannot hide her involvement in Luismi's arrest.