This question now has been answered. Emma was a daughter of Isaac Van Marter of Locke, Cayuga, NY and his wife Philinda Loomis. From Civil War Pension Files, Isaac and Philinda were both of Groton, Tompkins County, NY when they married there 24 Mar 1851. They had three children: Emma A. b. 2 Apr 1852; Sarah J. 25 Jul 1855; and Anna C. 8 Sep 1863. Sarah was born in PA, the other two in NY. Anna married a Mr. Champlin. Isaac was born in Tompkins or Seneca County, NY. He enlisted in the Union Army in late August of 1864, and was attached to Battery H of the 3rd NY Light Artillery Regt. He may have been with his unit during the battle of Chaffin's Farm 29 Sep - 1 Oct 1864, and was certainly with the unit for the rest of 1864, including Grant's Sixth Offensive of 27 Oct. Battery H was present at the fall of Petersburg 2 Apr 1865. Isaac died of typhoid fever 7 Jan 1865 in an Army Hospital at Point of Rocks, VA. By September 1866 Philinda had moved to Summerhill, Cayuga, NY with her daughters. She lived there without remarrying until her death 30 April 1914.
Isaac was the son of Gilbert Van Marter (1753-1819) and his wife Clarissa Bailey (c1800-1862). Gilbert was born in New Jersey, moved to Tompkins County, NY, then to Lodi, Seneca, NY. I don't know Clarissa's parentage, but from census records I believe she was related to Benjamin Bailey of Dryden.
Philinda was the daughter of Nathaniel Loomis (1790-1865) and Anna Reeves (1792-1863).