She's still alive in 1904 at the time he's originally discharged from the army
when he re-enlists in 1914 he lists 4 children b 1902 - 1912, Mary Ellen, Frederick James, Alice and Albert Edward, but then also has George Henry as one of his next of kin
Isabella would still have been under 18 and thus a child at this time, so I can only assume she's died