The sighting comes after it was revealed that Kardashian and the NBA player, 30, were reportedly still together when he allegedly impregnated the personal trainer in March.
"Khloé was upset to find out that he cheated again," a source told People. "She just can't believe that he is going to be a dad again."
"It's just a sad situation to her," the insider added. The Keeping Up With The Kardashians alum reportedly stayed with Thompson — whom she shares 3-year-old daughter True with — "because she always believed that he would change,'' and "wanted to keep the family intact for True."
As OK! previously reported, Nichols sued the former Sacramento Kings player — who also shares son Prince, 4, with ex Jordan Craig — for child support, reimbursement of medical expenses and pregnancy-related costs after it was revealed that the two had allegedly hooked up during one of Thompson's 30th birthday party celebrations in March.
On Friday, December 3, the fitness instructor announced that she gave birth to a baby boy named Angelou Kash Thompson. "I want to thank everyone for your well wishes," following the news of his birth.
"Me and baby are doing great. Right now my heart and mind is on focusing on the baby right now," she continued. "I am heartbroken that Angelou’s father doesn’t want to be in his life. I am hoping this lawsuit will bring us together and we can be a family."