EXCLUSIVE: Kris Jenner Reveals Why Kourtney Kardashian Is the Only Sister Without Her Own App

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Just about every Kardashian and Jenner sister has an app now, but not Kourtney!

Don't panic, though.

ET has learned that a Kourtney app is actually on the way -- she just wanted to take a little extra time to get it right, Kris Jenner is revealing exclusively to ET.

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"Kourtney's will be live next month," Kris says. "The girls have been working around the clock for a year on their apps and sites, and Kourtney gave birth to Reign in December. While everyone else was deep in production, she was taking time with her infant, nursing and caring for her children. So, she's a little behind, but, it is going to be fabulous."

Kourtney stepped out on Monday, looking absolutely ab-tastic in NYC, where the 36-year-old joined her sisters at Apple's "Meet the Developer" event in NYC, and she teased what's to come when her app launches.

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"Mine is more curated," said Kourtney. "I’m obsessed with interior design, so it’s a lot about that. I’m obsessed with being a mom. I have very specific ways of being a mom, as well."

"All my friends come to me with mom questions, so just sharing my favorite things," she continued. "There’s not one thing on [my app] that I’m not obsessed with thoroughly."

And the app already has one big fan: Kylie!

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"Her app's going to be amazing. She loves being a mom," Kylie told ET at Tuesday's Vera Wang NYFW Show. "She's spent a little more time on it."

The younger Jenner sister told ET in July that the purpose of the apps is to increase access the fans have to the sisters lives.

"Everyone wants to see, like, my makeup tips, and what I do with my hair, and this and that," she said. "So I just wanna do, like, tutorials, and what I use, because I feel like people are really interested in that."

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At $2.99 a month per app for premium content, they'd better be!

Get more details on the Kardashian Appstravaganza below.