Ross was seen without her wedding ring last month after Stewart confirmed her fling with the Snow White and the Huntsman director in a public apology to boyfriend Robert Pattinson.
Although she has apparently been going to family therapy sessions with Sanders and listening to his pleas for a second chance, Ross was seen out on an apparent date with an unknown man in London this week.
According to The Sun, the pair went from a party at the Serpentine Gallery in Kensington Gardens to a "romantic meal" in Soho, and left the restaurant holding hands.
The development follows reports that Stewart and Pattinson are back together again after realising that "they couldn't live without each other".
"Rob sees it as Kristen made a really stupid mistake," a source said. "After a lot of long tearful talks, they've worked it out."
Photo gallery - Kristen Stewart and Robert Pattinson's relationship: