The former Island ladies’ strokeplay champion, a title won at the age of 16, returned a gross score of 79, to top the scores by three strokes from club colleague James Draisey.
Royal Jersey also claimed third through Jack Cramsie, who returned a score of 83 in brutal windy conditions.
Keites’ success completed a hat-trick for her family as her elder brother, Stanley – now an Island men’s team golfer – registered back-to-back Gothard Trophy successes in 2015 and 2016.
In the handicap section, Robbie Forest carded a net score of 73 off 16 handicap, to beat Nick Lawrenson by two strokes.
The top eight in the Rathbones Junior Tour have qualified for the Jersey Junior Island Matchplay Championship. Quarter-final draw: Flora Keites v Sam Quail; Jon Chamberlain v Nick lawrenson; Jack Cramsie v Charlie Kiberd and James Draisey v Tom Chamberlain.
Matches are due to be completed by 12 May with the eventual champion representing Jersey in the CI final at L’Ancresse, in Guernsey, on 17 June.
The next Rathbones Junior Tour events is the Sid Guy Trophy at Royal Jersey on 3 June.