“Why was she even arrested by men claiming to want freedom from tyranny ???”
She and her husband were closely associated with the Mohawk Indians on the frontier during the Franch and Indian wars. With her husband deceased and the American Revolutionary War underway, she remained a Loyalist and used her position with the Mohawk, other Indians, Loyalists, and British on the frontier to conduct hostilities against the rebel settlers. Suffering cruel massacres at the hands of the Indians and the Loyalists, the rebels replied in kind. To keep her from using her influence with the Indians to conduct further raids and massacres, she and her Loyalist family members were imprisoned, but oftern cruelly so in the same manner being suffered by many Patriot families.
That husband of hers you mentioned, Captain Timothy McGinnis, just happened to have died at Lake George in Sept 1755 fighting the Indians and the French to save the butts of those same men who imprisoned her..
To keep her from using her influence with the Indians
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Well from Canada where she fled she was able to influence them a lot better thank you very much...
she convince many to go north to escape the eventually massacre that was coming after the war ended when the white men would want to go back to stealing the lands of the Indians err pushing the Indians ever westward out of the NY colony..