How does the relationship between Juno and Boyle change in Act 3?

The dichotomy between Juno and the "paycock" continues in Act III as we see how differently the two respond to suffering. While Boyle can think only of the effect Mary's plight will have on him and his reputation, Juno points out the ordeal their daughter will have to go through. Boyle is not even aware that Johnny has been killed, having left to escape his troubles through drink. Juno, however, undergoes a spiritual transformation as she realizes how selfish she has been in the past: “I forgot, Mary, I forgot; your poor oul’ selfish mother was only thinkin’ of herself… maybe I didn’t feel sorry enough for Mrs. Tancred when her poor son was found as Johnny’s been found now - because he was a Die-Hard." (71-2.) Thus strengthened, she decides to respond to tragedy in the way which will cause the most good, by leaving her lazy husband and instead helping Mary to raise her child.