Kourtney Kardashian is rumored to be unfazed by Scott Disick's blossoming relationship with a model half her age.

Sources close to the "Keeping Up With the Kardashians" reality star insist she isn't the least bit bothered by her ex's dalliances with 18-year-old model Lindsay Vrckovnik.

In recent days, the 32-year-old Disick, father of Kardashian's three young children, has been spotted hanging out with Vrckovnik everywhere from New York to Miami.

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

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

The increasingly unpredictable Disick and Vrckovnik were first publicly spotted together late last week spending a late night out together. The two partied the night away in New York, and were last seen returning to his hotel room around 6 a.m.

Sources described the pair as looking very much like a couple throughout the night.

"He kissed her a few times and was whispering in her ear with a smile on his face," a source added. "She seemed very into him but a little out of place, very uncomfortable when people were looking at her."

Kardashian and Disick split over the July Fourth holiday weekend, when he was spied cavorting with ex-girlfriend Chloe Bartoli in Monaco. The former couple has 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 previously told ET. "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."