Final answer:
The Loyalist socialite who mistreats her slaves Isabel and Ruth in New York City and is beaten by her husband is not named in the given texts; such characters are depicted in historical accounts and literature related to American slavery.
Step-by-step explanation:
The Loyalist socialite in New York City who mistreats her slaves, Isabel and Ruth, and is often beaten by her husband is not explicitly named in the references provided. However, characters similar to the one described often appear in historical narratives and fiction that deal with the period of American slavery and the Revolutionary War. Mentioned texts such as the experiences of Frederick Douglass and stories like that of Mary Silliman give insight into the plight and abuse of slaves by their owners, reflecting the historical context of the era.