It's a sartorial showdown!

An insider tells the new issue of Us Weekly (out now) that Halle Berry, 45, has been fuming because her powerhouse stylist Deb Waknin constantly caters to another A-list client: Sandra Bullock, 47.

Waknin was "spending all her time with Sandra and not giving Halle any attention," the insider explains. "Halle got jealous because when she needed Deb, she was always with Sandra."

PHOTOS: Halle Berry's age-defying style

Newly engaged Berry -- mom to Nahla, 4, with ex Gabriel Aubry -- then dissed Waknin and used Heidi Klum's stylist Maryam Malakpour on two occasions. (A rep for Berry denies any rift, insisting, "Deb and Halle have worked together on and off for years.")

As for Berry's relationship with Bullock, mom to son Louis, 2? "There's no jealousy between them," the insider tells Us. "They are friends."

PHOTOS: Famous celebrity feuds

For more on the fashionista face-off, watch the Hot Stuff video (above), as told by Us Weekly Senior Editor Ian Drew.

Also in the roundup: Peter Facinelli takes the high road as Jennie Garth blabs about their split, Emma Roberts and Chord Overstreet rekindle the flame, and much more!

Get more Us! Follow us on Twitter, Friend us on Facebook, Subscribe to Us Weekly