Euphoria and The White Lotus star Sweeney sparked confusion when she attended the wedding of Sanchez and Bezos in Venice in June.
A report from Page Six said Sweeney went to “pay respects” to Bezos because she was set to act in an Amazon MGM Studios film.
Variety reported she signed on to star in the film adaptation of the hit video game Split Fiction.
Amazon MGM Studios picked up the project in June, which “seemingly” led to Sweeney’s wedding invite, the Daily Mail reported.
A source told Page Six that Sweeney “is not friends with either one of them”, but Sanchez’s attendance at her birthday indicates the two have since formed a friendship.
Actor Glen Powell, DJ Diplo and rapper Wiz Khalifa were also seen in photos of the party Sweeney posted online.
Powell starred alongside Sweeney in the 2023 romantic comedy Anyone But You.
The pair’s chemistry during press for the film sparked dating rumours.
Actor Ashton Kutcher was also seen in a photo from the party on Sweeney’s Instagram.
Nasa decorations and a galaxy-decorated cake featured in the pictures.
Sweeney recently faced backlash over a controversial American Eagle advertisement, which some criticised for promoting eugenics.
Earlier this month, she launched a collaboration with Jimmy Choo.
