Complex sentence: Carmel keeps pushing her until she breaks and admits that she and Calvin slept together, and that Calvin is the baby's father and she also inadvertently lets Myra know that Mercedes was having an affair with Calvin.
Split into simpler sentences: Carmel keeps pushing her until she breaks and admits that she and Calvin slept together, and that Calvin is the baby's father. She also, inadvertently, lets Myra know that Mercedes was having an affair with Calvin.