Kourtney Kardashian Reacts to Scott Disick's 18-Year-Old Model Girlfriend

Kourtney Kardashian "isn't fazed" by Scott Disick's new, much younger girl.

Kourtney Kardashian is moving on from Scott Disick -- and actually isn't bothered at all by the 32-year-old's latest gal-pal, 18-year-old model Lindsay Vrckovnik, a source close to the 36-year-old reality star tells ET.

Scott has been spotted with the blonde beauty multiple times in both New York City and Miami, Florida recently, not exactly going undercover with their relationship.

"Kourtney surprisingly isn't fazed by this at all," the source says. "She's moving on. She knows it's just a fling."

WATCH: EXCLUSIVE -- Scott Disick's Rumored New Girlfriend is 18-Year-Old Model Lindsay Vrckovnik

"She's trying hard to ignore it and just focus on the kids," the source adds. "She knows they'll never get back together."

News of Scott's new girl broke last Thursday, when the pair was spotted having a late night out together. The two were snapped at a bar in NYC before going to a house party, went to 1 Oak nightclub until 4 a.m., then hit up another house party before returning to Scott's hotel at around 6 a.m.

"Scott was hanging with this girl all night," a source inside the club told ET. "He had his arm around her and they looked very couple-y. He kissed her a few times and was whispering in her ear with a smile on his face. She seemed very into him but a little out of place, very uncomfortable when people were looking at her."

By the looks of it, it's clearly over between Kourtney and Scott, who split over the Fourth of July weekend after nine years together. The exes have three kids together -- 5-year-old Mason, 4-year-old Penelope and 9-month-old Reign.

"Scott sees the kids whenever he wants to," a source to the former couple told ET last month. "Despite all of Scott's addiction problems, he is a great dad and loves those kids with all his heart, and they are obsessed with him. He comes to her house to see them."

"[But] Kourtney is not taking Scott back -- never, as of right now," the source added. "Kourtney has been through a lot of drama with Scott over the years but it's for real this time."

WATCH: Scott Disick Moves on From Kourtney Kardashian With a Hot Blonde in New York City -- See the Pics

Watch the video below for more on Scott and his new girlfriend showing off her bikini bod in Miami last Friday.