She was in Los Angeles by 1890. Here are newspaper articles that mention her:
http://chroniclingamerica.loc.gov/lccn/sn84025968/1890-05-20...

Los Angeles herald., May 20, 1890, Page 3, Image 3

Boys’ Aid Society. A New Organization Formed Yesterday. About twenty ladies gathered yesterday afternoon in the recently opened reading-room at 229 South Main street, for the purpose of organizing a boys’ aid society for the benefit of the newsboys and others in Los Angeles needing the assistance of kindly hands to obtain a start in life. … The following were among the ladies present: Mrs. Shinkwin. . . .


http://chroniclingamerica.loc.gov/lccn/sn84025968/1890-05-21...

Los Angeles herald., May 21, 1890, Page 8, Image 8

News Notes. A lady wishes it stated that there were seventy ladies, not twenty, in attendance at the organization of the boy’s aid society on Monday. Mrs. Shinkwin, who has, in connection with Mrs. Stillman Drane, been maintaining the boy’s reading room on Third street for some time past, has just purchased a house and lot opposite the power house of the Second-street cable road, where she proposes to establish a home for boys. The only requirement for admission will be that the boy shall be homeless, friendless, and need help.

http://chroniclingamerica.loc.gov/lccn/sn84025968/1890-06-27...

Los Angeles herald., June 27, 1890, Page 2, Image 2

Boys‘ Aid Society. Important Meeting Yesterday Afternoon. There was a large attendance of the members at the meeting of the Boys’ Aid Society, No. 229 South Main street, yesterday afternoon. In the absence of the president, Mrs. Stillman Drane called the meeting to order. … The following committees were appointed by the president: … Household—Mrs. Shinkwin, … The society then adjourned to meet at the call of the president.

http://chroniclingamerica.loc.gov/lccn/sn85042462/1905-12-29...

Los Angeles herald., December 29, 1905, Page 8, Image 8
Incorporations. Shinkwin Young Men’s Home. Directors: F. A. Seymour, M. L. Godfrey, Curtis D. Wilbur and others. Capital stock, none.

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Los Angeles Times, 27 Oct 1909. Obituaries.

SHINKEVER. At No. 1211 Sapphire street, October 25, 1909, Anna M. Shinkever, aged 78 years. Funeral at the chapel of Bresee Bros., No. 855 South Figueroa, Wednesday at 2:30. Friends invited.

http://chroniclingamerica.loc.gov/lccn/sn85042462/1909-11-18...

Los Angeles herald., November 18, 1909, Page 16, Image 16

Woman Provides for Hotel for Young Men. Thirty Thousand-Dollar Bequest is Made in Will of Mrs. A. M. Shinkwin. The will of Mrs. A. M. Shinkwin, who died October 25, was filed for probate yesterday, and among its bequests is one of $30,000 for the building and maintenance of a hotel on property adjoining her old home of Saphhire street. The will provides the hotel shall be for the exclusive use of young men of moderate means and to free them from the evil associations of cheap lodging houses. The executors of the will are Simon Stuart, Harry Chandler, C. A. Jeffers and H. C. Whitman, and Mrs. Shinkwin in her will requests them to appoint six other men of good standing in the city and the ten to act as a board of managers of the hotel. No estimate concerning the value of Mrs. Shinkwin’s estate is given in the petition for probate accompanying the will.

http://chroniclingamerica.loc.gov/lccn/sn85042462/1910-12-14...

Los Angeles herald., December 14, 1910, Page 5, Image 5

More Contests Filed Against Shinkwin Estate. Brother Attacks $80,000 Bequest to Found Home. Two contests involving property valued at about $85,000 and deeds and the will of Mrs. Annie M. Shinkwin, who died October 25, 1909, were filed yesterday in the superior court. After the death of Mrs. Shinkwin a will was found by which she devised to a board of trustees composed of Harry Chandler, Lyman J. Stewart and others all of the property of which she was possessed, her object being that it should be used to found a home for young men. Before her death, however, Mrs. Shinkwin has deeded to the same board of trustees the major portion of her property, the object being the same as that expressed in her last testament. The actions filed yesterday, one in the probate department and the other in the regular channel of civil cases, ask that the probate of the will be revoked and that the deeds be set aside. W. H. Gibbs, a brother of the dead woman, and others of her relatives are the petitioners, alleging that she was of unsound mind when she made her will and executed the deeds, having been a user of drugs. Another and similar contest has been pending against the deeds and the will for a considerable period. It is that of Mrs. Clara H. Moore and Frank K. Amie, sister and brother, who allege that they are both the natural and adopted children of the dead woman. They assert that when they were quite small she placed them in an orphans’ home and later was required by law to adopt them when she wanted them with her again.