Final answer:
Mabel Todd made comments about Emily's behavior and disposition, which the narrator finds unusual and uncharacteristic. Mildred Todd is behaving in an uncharacteristically irritable and bitter manner, and the narrator doesn't know why.
Step-by-step explanation:
Mabel Todd, mentioned in the passage, made comments about Emily's disposition and behavior. The narrator of the passage mentions that Mildred Todd's behavior was unusual and uncharacteristic, which surprised him. He describes her as being irritable and having a bitter edge to her sweet mouth. The narrator is puzzled by Mildred's change in behavior and doesn't know what is causing it.