Well, she wasn't there to see that it was Jack taking charge of the rescue. After Will broke him out of jail, Jack took the lead and Will followed. If you watch it from only Will's point of view, he doesn't do a lot of pirate things after helping Jack steal the ship, but if you watch from Liz's point, you know nothing in between seeing Will as you're being dragged away and when you see him after you told Barbossa you weren't the child of Bootstrap Bill.
I have also wondered why Will doesn't tell Liz that he "Sprung a man from jail, commandeered a ship of the Fleet, sailed with a buccaneer crew out of Tortuga" to prove to her he is a pirate, or to let her know how much he has proven he loves her by his actions.
He does not tell her how much Jack helped to precipitate her rescue. She does not find out til she is back on the Dauntless with Gibbs and crew.
TnT should have had him throw in with Jack to facilitate both objectives if they wanted him to be a "pirate movie pirate", and the true love story for Lizzie.