I debated if I should comment on this. Race riding is a weak spot for me.
But I watched the race and saw Prat save every inch of ground on the first turn. Commenced her rally outside of Bonny South early into the second turn and ran up behind Royal Flag, who wasn't moving as fast as she was at that point. Having good momentum at that point Prat really had no choice but to go outside that rival. The turn was almost over anyway, and the stretch is approaching.
Agree entering the stretch Dunbar was very wide, but I don't believe Flavien's ride cost her much if anything. Going inside always means possibly getting stopped.