I just read through the long newspaper account of the trial, and the defendant had written Florence a letter, in which he referenced a Harry, and her "Dad". Although the letter wasn't included in the article, the lawyers did ask her for clarification. She stated that Harry was her Uncle Henry, and "Dad" was her grandfather, as she was raised by her grandparents.
As a sidenote, the defendant also murdered one of the Constables trying to arrest him, and had wrongly anticipated that Florence would be with Henry, as he planned on killing both Florence and Henry.
Another article mentioned that first banns had been read (for Florence and Louis Hamilton), but as banns don't include the father's name, I guess that doesn't help.
(Edit: in checking for banns, the first two banns were read; the third was "withdrawn on account of murder")