"She's gone to another level and this race will tighten her up for the Guineas."
The daughter of So You Think jumped well from the gates before she was allowed to drift towards the tail of the field by rider Racha Cuneen to get closer to the fence.
"We told Racha not to panic and ease back and it's not always easy to come from there at Ashburton so it was a very good effort," Brown said.
When the field fanned out on straightening, Cuneen was able to pick a path between runners and a willing La Diosa surged through to win going away by a length.
"I had to ride for luck and we got the splits and she did all the rest," he said.
Runner-up Heroic Valour, who has remained steady at $6 in the Group One Sothys NZ 2000 Guineas market, looked set to return to his winning ways when he hit the front on straightening, but he had no answer to the filly's finishing burst.
Savile Row made the pace and he rallied well for third ahead of Sweepstake, whose 1000 Guineas price has come in from $31 to $14. Sweet Leader finished fifth after having his chance.
- NZ Racing Desk