Jennifer Garner Happily Heads to Gym Following Ben Affleck's Date Night With Lindsay Shookus

Jennifer Garner does not seem fazed that Ben Affleck is spending time with another woman.

While her estranged husband had a night out with Saturday Night Live producer Lindsay Shookus on Monday, the 45-year-old actress woke up bright and early the following morning to work out at Body by Simone in Brentwood, California. Garner -- wearing an all-black athleisure outfit and bright blue shoes -- was seen happily chatting away on her phone as she headed into the establishment.

WATCH: Jennifer Garner Smiles Big in First Sighting Since Ben Affleck's New Girlfriend Revealed

A source tells ET that the mother of three is a regular at Body by Simone, and while she usually takes private sessions, she recently attended a group class that Simone was teaching and even chose to work out in the front row. The source says that Garner is always kind to the other clientele, adding that she's "positive, friendly, confident and really into the workout." The source also notes that the Alias star is not shy about asking questions regarding form and technique and is almost always makeup-free.

As for Affleck and Shookus, another source tells ET that the two do not want to keep their relationship a secret. The two were most recently spotted sharing a laugh while leaving Starbucks, and later went to dinner at Beech Street Café in Pacific Palisades, California.

MORE: When Did Ben Affleck and Lindsay Shookus Start Dating? The Complicated Timeline of Their Romance

"Lindsay is a super private person, but she’s happy with where she is in her life right now," the source said. "No reason but to smile."

Ben Affleck Steps Out With New Girlfriend Lindsay Shookus After Relationship Goes Public

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