Generally, with the eastern European surnames, a woman's name would end in "a" while the same surname for a male in her family would end in "i." So, if you are researching an Anna Karwowska, then you should definitely be looking for her male relatives under Karwowski, and her female relatives under Karwowska. You might also consider researching Karwowsky as well.
I am researching the surname Karwowska as well, but my gggrandmother's name was Kamilla, and she grew up in Utica, New York. I'm sorry that I can't offer you any help on your specific line.