Placed behind Catchy in the Group II VRC Danehill Stakes at Flemington and behind Merchant Navy the Group III MRC McNeill Stakes at Caulfield, Booker advances her record to two wins, two seconds and a third from just five starts with earnings of $286,000.
"She got a bit of a speed pedigree, but she's got a lot of stamina there as well," Dunn said.
"Getting to the bend I was under a little bit of pressure, she came back under me good and she wanted to lay out a little bit like she did the other day, but it was a good effort against some really top-quality fillies.
"Today we wanted to take the race by the scruff of the neck and try and try and be there, we're going to the mile next time so make sure that she could run it.
"It is a really good box to tick and hopefully she can win the Thousand Guineas."
Matthew Ellerton saidBooker will likely press on to the Group 1 MRC Thousand Guineas at Caulfield in a fortnight.
"She did a bit of work early, we were always going to be positive and she was good enough to hold on," Ellerton said.
"She is a filly that doesn't get under much pressure at home so she is probably still learning to let down. Both starts here she's wobbled around the bend, she is just getting used to that race day pressure I think.
"She probably didn't want much further today, but she did do a little bit of work early and she does have a bit of improvement to come."
Booker is the first foal of Noondie, a three-quarter sister by Flying Spur to stakes-winner Tranquility from stakes-winner Creatrix.
Noondie has a yearling full brother to Booker and has foaled this spring producing a colt by Starspangledbanner.