© Rex Features
The Bridget Jones actress, who was first romantically linked to The A Team star Cooper in August last year, reportedly spent two hours looking through wedding dresses in a Caroline Herrera shop.
An onlooker told the New York Post: "She just kept smiling when asked if she is getting married."
Zellweger reportedly later left the West Hollywood boutique with a bag of unidentified garments.
Cooper was married to actress Jennifer Esposito for four months, while 41-year-old Zellweger's marriage to singer Kenny Chesney was annulled.
