I started with the predictable Google search: ["Pearl Johnson" anarchist]

The top result is your question ;), but after that, there are several Google books including Anarchist Voices by Paul Avrich, where Johnson's daughter gives this short description:

Mother - Pearl Johnson - was the daughter of a New England couple, Horace Johnson and Florence Hull, one of four daughters of Moses Hull, a minister of advanced views who became a well-known spiritualist. Pearl went to the Sunrise Club in New York, and knew Bea Schumm. It was George Schumm who suggested her to father to work in his bookshop a few years before I was born. One of mother's sisters was Dr. Bertha Johnson. Fred Schulder, who worked as a salesman for Liberty, was Aunty Bertha's boyfriend. His son with Adeline Champney, Horace Champney, was the Quaker who sailed a boat to Vietnam a few years ago to protest against the war.

The rest of Oriole's interview is available in html, and appears to be faithfully reproduced on the 1998 nightmare of a website by Uncle Taz, Tarjei Straume.

I sent you this article I found in ProQuest Historical Newspapers:

From the New York Herald.. "THEY SCORN CONVENTION :Anarchist "Comrades" Give Birthday Party for Month-Old Daughter.." The Washington Post (1877-1954), January 4, 1909.

I found this article about Tucker on JSTOR that mentions Johnson a few times:

Benjamin R. Tucker: Individualist and Anarchist. Charles A. Madison. The New England Quarterly, Vol. 16, No. 3 (Sep., 1943), pp. 444-467

Since I know you have access to Columbia databases, I recommend you try those I suggest on my Women's Studies Research Guide. Search ["pearl Johnson"].

I'll check the Encyclopedia of Political Anarchy when I get back to the library on Monday. Please remind me!

Also, write to Julie Herrada, Curator of the Labadie Collection at the University of Michigan to see what she recommends. I see they have a few things from their online finding aid.