Jack Hatfield (1912-1927), in the 500 yards and one mile freestyle, and Adrian Moorhouse (1981-1991), in the 100m breaststroke, are the only other competitors to have won the same event on nine occasions in the ASA's 125-year history.
Osher's latest victory means the Barnet Copthall 25-year-old will go to next month's Commonwealth Games in better heart than she could have hoped for only a few weeks ago.
'I had been feeling tired and run down since Christmas and I went to see a physiologist during the British Olympic training camp in Florida last month. He said I had been overtraining,' Osher said. 'So I have now cut down and I'm feeling a lot sharper. I'm glad I've got it sorted out before the Commonwealth.'
Osher won in 2:16.38, ahead of Emma Tattam of Portsmouth, whose time of 2.16.39 secured her Commonwealth Games place. Tattam had earlier beaten Osher in a heat.
Joanne Deakins was third in 2:16.85. Both Osher and Deakins had been preselected for Victoria and all the 200m places are now filled.
Also on their way to Victoria are Steve Mellor, of Macclesfield, following his victory in the men's 400m freestyle, and Matthew O'Connor, from the City of Leeds club, after his third place inside the required qualifying time in the men's 200m backstroke.
The women's 200m backstroke heats also produced a paralympic world record. Sarah Bailey, 16, from Stockport Metro, took almost two seconds off her own world mark for the amputee section with a time of 2min 36.56sec.