The Playboy model, 22, walked her pooch in Los Angeles while wearing a black leotard top and matching miniskirt, which she paired with black sneakers and matching sunglasses.
Sexton and Affleck, 46, had been spending time together in recent days amid news that he and Lindsay Shookus, 38, had called it quits after one year of dating. Sexton and Affleck shared dinner together at Nobu restaurant in Malibu and were later photographed grabbing Jack in the Box in Santa Monica last weekend.
“He is happy being able to date who he wants and not feel tied down to a serious relationship,” a source told PEOPLE at the time.
But they were far apart on Wednesday, as she hit a Malibu beach while Affleck’s ex Jennifer Garner — with whom he shares children Violet, 12, Seraphina, 9, and Samuel, 6 — was seen driving him to rehab.
PEOPLE confirmed Affleck had entered rehab for alcohol addiction on Wednesday, with a source saying, “He is seeking treatment. He knew he needed help and was vocal about it.”
A second source tells PEOPLE in this week’s issue Garner’s focus remains on their children.
“Is she happy about him hanging out with a very young Playboy model? Certainly not,” the source said. “But her concern right now is not who he is dating. What she ultimately cares about is his sobriety and whether she can rely on him to co-parent.”
Meanwhile, before entering rehab for a third time, Affleck had been “working incredibly hard for the last year” to remain sober, a source close to the actor tells PEOPLE.
“Addiction is not something that goes away. Every day is a battle for recovering addicts, they are fighting for their sobriety and to lead healthy, balanced lives every day,” the source said.
Affleck had frequently been sighted visiting outpatient treatment centers in L.A. “Ben has been working incredibly hard for the last year to follow a streamlined program designed for him and his journey,” the source explained. “He has been attending countless meetings, has continued to work with sober coaches and does his best to follow through with the things that will help him maintain his health.”
The source added that Affleck was aware he needed help and did the right thing in reaching out.
“One of the key elements with taking control of your addiction is knowing when to seek help, which he did, and it is a major step in the right direction,” the source said.