The 31-year-old star recently spoke kindly about Lamar, but insiders say yesterday's incident is making her "reevaluate" her opinion of him.
The source added to People magazine: "The thing is, despite everything that had happened with Lamar, she acknowledges that it overall was a good time in her life and he was a good guy with demons. This is definitely making her reevaluate and move on."
While Lamar, who was dumped after four years of marriage amid allegations he was addicted to drugs and cheating on her, insists he never ambushed Khloe, onlookers claimed he shouted at her, though the reality TV star initially attempted to ignore him, but screamed: "Get off of me, get off of me. Stop. Stop," after the former LA Lakers star grabbed her arm.
Defending himself, Lamar told TMZ: "Nobody got followed, nobody got hassled, nobody got harassed, nobody got grabbed on, none of that. I don't believe in following people around.
"I don't Twitter. I don't Instagram. Me and that girl fell in love. That's our business. ... Do not disrespect my space, do not disrespect my character, because that's what y'all been doing. And from day one, even if half the things were true, even if half of them were true, people know who I am and y'all have discredited me, beat me down, took my confidence, took everything away from me."
Khloé, who recently started dating NBA star James Harden, 25, and went public with their romance at her half-sister Kylie Jenner's 18th birthday party last weekend, then left the scene in her car.
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