Complex sentence: Gabrielle was the final housewife to be greeted by the group, she was dressed in her underwear, after just having sex with Carlos, when Mary Alice, Susan, Lynette and Bree walked in.
Split into simpler sentences: Gabrielle was the final housewife to be greeted by the group. She and Carlos were only wearing underwear as they had just had sex when Mary Alice, Susan, Lynette and Bree walked in.