The singer-and-actress - who announced her engagement to ice hockey player Mike Comrie after a trip to Hawaii in February - is rumoured to be planning to tie the knot in the next two days at the beautiful San Ysidro Ranch in Santa Barbara, California.
According to a source, the couple chose the ranch - where the late American President John F. Kennedy and his wife Jackie spent their honeymoon - for "its sense of old Hollywood glamour and romantic style".
The source added to In Touch Weekly magazine: "No detail is going to be spared for their big day."
Celebrity wedding planner Mindy Weiss - whose former clients include Gwen Stefani, Jessica Simpson and Adam Sandler - is organising the "quiet affair".
Groom-to-be Mike - who proposed with a $1 million engagement ring - fuelled speculation the ceremony is taking place thisweekend after he was spotted celebrating his last days as a single man with a bachelor party at Los Angeles club Trousdale on 10.08.10.
An onlooker told the New York Post newspaper: "He was with seven friends, and they sat in a VIP booth drinking vodka. They had a great time, but Mike was pretty well behaved."
Hilary, 22, has been getting ready for her big day by working out six days a week, as well as taking dance lessons with Mike, 29.
Hilary previously revealed she is worried about her wedding dress "overwhelming" her petite frame.
She said: "I want it to be girlie and kind of on the bigger side but not too overwhelming because I`m so small. I mean, people would be like, `Whoa, cupcake!-"