The 38-year-old Keeping Up with the Kardashians sister and her ex still remain in each other's lives due to the three children they share: Mason, 8, Penelope, 5, and Reign, 2. But a source close to Richie says she believes Kardashian is also still in love with her ex.
"Sofia can't believe someone Kourtney's age would still be such a mean girl. She's convinced Kourtney's still in love with Scott and that's the reason she's being so awful, but there's still no excuse," the source told HollywoodLife.com Wednesday.
Kardashian's alleged pettiness extended to mom Kris Jenner's annual Christmas Eve party, to which she invited current boyfriend Younes Bendjima, 24, and Disick. Richie, meanwhile, was allegedly not invited.
"Sofia hasn't done a thing to deserve the way she's being treated," the insider continued.
Kardashian's reported behavior may not be having the intended effect, however.
"It's hurtful for Sofia but it's not doing any damage to her and Scott. Actually it's kind of pushing them together because they feel like it's them against the world," the source added.
"Since returning to L.A., Scott and Sofia are inseparable. They are spending every day together. Sofia seems smitten," a source told PEOPLE in September, when they made their relationship official.
However, a source in October said the reality TV celeb isn't concerned with her ex's relationship.
"At this point Kourtney isn't interested in Scott as a romantic partner," a source told Entertainment Tonight. "All that matters to her is that he is a good father to their children. He loves his kids and he's good to them. She does not care who he dates or who he spends his time with."
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