According to the source, Richie, 21, is "still processing the breakup."
"It was a serious relationship, not some fling, and she was there for Scott through some tough times," says the source. "It hurts to see all the speculation about Scott and Kourtney, but she is so young and gets so much attention. She'll be totally fine."
A rep for Richie did not respond to PEOPLE's request for comment.
Their split came after Disick, 37, sought treatment in rehab in late April. When a photo of the star inside the rehab center was leaked online on May 4, just under a week after he'd arrived at the Colorado treatment facility, he checked himself out and flew back to Los Angeles.
A source told PEOPLE at the time that Disick and Richie were taking a break "so Scott can just focus on the most important things in his life — his health and his kids."
"Scott is working on his issues. Sofia is hanging out with friends," that source explained. "It was Sofia's choice to take a break."
Since then, Disick has maintained a relatively low profile, though he's been spending time with Kardashian and their sons Reign, 5, and Mason, 10, and daughter Penelope, 7. Over the weekend, Kardashian, 41, dedicated a sweet Father's Day tribute to her ex.
"Happy Father's Day, thankful for you and these three special ones," she captioned a photo of the family.
As for Disick's health? A source told PEOPLE after his rehab stint that the father of three is "committed to getting better" and "talking to a lot of people who can give him psychological, emotional, physical and spiritual health."
Although the source declined to specify the nature of Disick's issues, he has struggled with alcohol abuse in the past. While he has not publicly commented on the recent rehab stint, his attorney Marty Singer denied reports that his client entered treatment because of cocaine or alcohol abuse, maintaining it was to "work on his past traumas."