Kourtney Kardashian Snaps Sexy Mirror Selfie in SKIMS Valentine's Day Collection Bra and Thong

Kourtney Kardashian/Instagram

Kourtney Kardashian wasn't invited to be a part of Kim Kardashian West's Valentine's Day SKIMS campaign with sisters Kendall and Kylie Jenner. But that didn't stop the star from doing her own mini-photo shoot wearing the sexy lingerie at home as a way to poke fun at the sisterly snub.

Kourtney, 41, showed some skin in the Instagram selfie, posing on her knees on the floor of her bedroom closet wearing the fiery red SKIMS Fits Everybody Scoop Neck Bra and the barely-there SKIMS Fits Everybody Micro Thong, which sold out quickly after launching on Valentine's Day. She accessorized with an edgy skull and crossbones necklace (perhaps a style nod to rocker boyfriend Travis Barker?).

She couldn't help but call out her sisters in the caption writing, "Since I wasn't invited to the sister shoot ..."

Kim, the SKIMS Solutionwear founder, shot a sexy Valentine's Day campaign alongside sisters Kendall, 25, and Kylie, 23, to promote the launch last week.

Kourtney Kardashian/Instagram

Kourtney took the joke a step further by reposting a fan's artwork that Photoshopped the Poosh founder onto the SKIMS campaign image with Kim, Kendall and Kylie.

RELATED: Kim Kardashian Models with Sisters Kendall and Kylie Jenner in Sexy SKIMS Valentine's Day Campaign

Kourtney gave a glimpse into her romantic Valentine's Day with former Blink-182 drummer and new boyfriend Barker when she posed in revealing red La Perla lingerie over the weekend.

kourtney kardashian/instagram

Kourtney spent her day with Barker, who she started dating recently after years of friendship. The couple shared matching photos of a crackling fireplace, both on their Instagram Stories.

Two days after their Valentine's Day celebrations, Kourtney and Barker made their relationship public on social media. The mom of three shared a photo of the couple's hands clasped together on Instagram. While she didn't add a caption to the image, Barker, 45, shared the post on his Instagram Stories.

RELATED VIDEO: Kourtney Kardashian Is Dating Travis Barker, Source Says

Kourtney Kardashian Is Dating Travis Barker: Source

"They've been friends for a long time but it's turned romantic," a source tells PEOPLE

The duo hinted at their relationship, which a source confirmed to PEOPLE in January. They have been friends for years and recently were spotted out and about in Los Angeles together, but Kourtney's photo on Tuesday is the first time either have posted a photo together.

Kourtney Kardashian/instagram

A source previously told PEOPLE that Barker has been crushing on Kourtney "for a long time."

"He's liked her for a long time and she just got more open to the idea. He's a good guy and a really great dad," the source told PEOPLE. "Her family and friends all really like him. Their kids all get along too, which is sweet."

Kourtney and ex Scott Disick co-parent their three kids: Mason, 11, Penelope, 8, and Reign, 6. Barker shares children Atiana, 21, Landon, 17, and Alabama, 15, with his ex-wife, Shanna Moakler.