Hamlin, 20, shared a series of pictures on her Instagram feed Monday, beginning with one of her flashing a middle finger at the camera.
A few days earlier, on Thursday, Disick, 38, was seen with a blonde woman outside Hyde Sunset in the West Hollywood neighborhood of Los Angeles. The woman has been identified by Page Six and the Daily Mail as model Elizabeth Grace Lindley.
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Disick and Hamlin split in early September following nearly a year of dating. A source previously told PEOPLE the couple went "through a rocky patch" after Disick allegedly shaded ex Kourtney Kardashian in leaked DMs to Younes Bendjima, another ex of hers.
"The split from Amelia was sudden and unexpected. He was pretty shocked about it. He has slowly been dating, but is not serious with anyone," another insider told PEOPLE of Disick earlier this month. "He seems good though. He is around for his kids a lot. He loves spending time with them."
Joe Scarnici/Getty; Jean Baptiste Lacroix/Getty Scott Disick and Amelia Hamlin
His recent outing was also the first sighting of him since news broke of Kardashian's engagement to Travis Barker. The Blink-182 drummer, 45, popped the question on Oct. 17 on a beach in Montecito, California.
Last week, a source told PEOPLE Disick was "not happy" about the engagement, adding: "Scott never approved of Kourtney dating Travis. He has struggled with their relationship. He always had this idea that he and Kourtney would eventually get back together. He was pretty shocked when he found out that she was dating Travis."
Another insider said the Talentless clothing mogul was "distancing himself from the [Kardashian] family" in order to "process" the news.
"It's not about them, it's not about Kourtney," the source said. "It's about him needing some time to process this and deal with it on his own, without them. He'll come around soon."
Watch: Scott Disick ready to find love again