Here's how she manages to achieve the incredible packing feat.
First, Grant says you should roll your clothes to save space.
Packing smaller, rolled-up items of clothes in ziplock bags will keep them organised as well as let you compress the clothes by letting the air out - kind of like mini-vacuum bags. She also suggests opting for lightweight clothes.
Rolled-up socks are packed inside shoes - which save space as well as helping keep the shape of the shoes - and are bound together with elastic bands.
With the clothes hanging on the rack, Rachel suggests folding similar-sized clothes together, and she packs them in packing cubes.
Then she begins loading everything into the suitcase.
Heavy items go at the bottom, while gradually building up to the lighter items and loose accessories.
Brava, Rachel - those of us who are prone to taking too many clothes on holidays can't thank you enough.