As the face of Bobbi Brown, Katie is making her mark in the beauty world and has grown close to the cosmetic guru who she has called an "incredible woman" and a "lovely person" since their collaboration started.
The powerful duo have created the Bobbi & Katie line, which is made up of a brush set, eight eye shadows, two pot rouges and a mini eye pencil, the latter of which Katie put forward herself.
The neutral colours in the palette are said to be inspired by an old pink and brown journal that Katie has, and embraces Bobbi's very natural approach to beauty.
"Our objective was to do something that is very helpful to all women," said Katie, speaking to WWD. "You can put it on in the back of a cab, you can put it on in your bathroom at home, you can put it on in the parking lot at your child's soccer game.
'I'm busy, Bobbi's busy. I don't know a woman who isn't busy, and you need that quick fix.'
Katie and Bobbie's business partnership seems to be going from strength to strength ever since the Batman Begins actress was chosen to front the make-up brand, and both women speak in constant praise of each other.
"I didn't hire a celebrity," said Bobbi, at the time of the collaboration. "I hired a woman who I think is really cool, who is down to earth, who sparkles when she enters a room, and she photographs really well."
Katie, meanwhile, admitted she has always been a fan of the brand and Bobbi's philosophy of easy-to-apply make-up.
"I really like her philosophy that make-up makes you feel beautiful," said Katie. "I've always been a fan of her make-up, because it's so easy to apply. Her colour palettes aren't extreme, so when I first started wearing make-up it felt comfortable and I didn't feel like I had too much on, which can happen."
The Bobbie & Katie line will launch in September, followed by a skincare range.