Final answer:
Melba was likely not invited to Marsha's party due to a lack of popularity and social skills, mirroringly similar to Bernice's situation in the story's context.
Step-by-step explanation:
The reason Melba was not invited to Marsha's party is not directly mentioned in the provided text. However, the context suggests that social dynamics and popularity play a significant role in the decisions regarding social invitations in the story. The character Marjorie expresses frustration about Bernice's lack of social skills and her inability to engage men in conversation, which seems to affect her popularity negatively. Marjorie attempts to give Bernice hints on how to improve her appeal but faces resistance, implying a tension between them that could mirror why Melba might not be invited to Marsha's party if their relationship is similar.