In Chapter 29, how does Myrtle prove that she cares about her daughter?

When the fight between Miles and Faith becomes physical, Myrtle chooses to back Faith by striking Miles and sending him away. Without an adult male in the family and with the knowledge that Dr. Jacklers is likely going to report that Erasmus committed suicide, Myrtle could have justified the decision to force Faith to hand over Erasmus's papers. The fact that she does not is a statement of how much she loves Faith, though their relationship is often difficult.