23 Answers:
1) Major Henry Rathbone and his fiancee, Clara Harris, daughter of Senator Ira Harris
2) She was killed by her husband, Major Henry Rathbone, who after the assassination developed a mental illness. While he once tried (not for the first time) to attack their children, Clara rushed to their aid and was first shot, then stabbed to death by Rathbone in a fit of insanity.
3) Hannover, Germany - Stadtfriedhof Engesohde (Engesohde Cemetery), but the grave no longer exists