I purchased in Santa Rosa, CA the subject undated studio portrait of a young woman identified on the back of the mount:
"Mollie Angeroth Pfost 2nd sister of Wm Angeroth"
The only likely candidate for this individual that I can find is Mary L. Angeroth, born about 1872 in MO, the daughter of Max Angeroth, born about 1833 in Russia, and Evaline (maiden name unknown), born about 1843 in KY. She appears in Public Member Trees posted on ancestry.com. She is listed in the 1880 U.S. Census data for Derr Creek Township, Phillips Co., KS; and the 1895 Kansas State Census data for Belmont Township, Stockton Post Office, Rooks Co., KS. On 12 Feb 1890, she married Alonzo Franklin Pfost, born 14 Jan 1869 in Bates Co., MO, died 13 Dec 1951 in Middletown, Canyon Co., ID. The couple had two children: Myrtle C. Pfost, born 19 Nov 1890 in KS, and Mildred Vern Pfost, born 5 Mar 1892 in KS, died 28 Dec 1974 in Portland, Multnomah Co., OR.