"It's pretty serious," the source said.
Hedison dated Ellen Degeneres from 2001 to 2004, shortly after she broke up with Anne Heche. She also played Dylan Moreland on Showtime's "The L Word."
In a rambling acceptance speech at the Golden Globes last January, Foster said she came out "about a thousand years ago back in the stone age," and thanked her ex Cydney Bernard. Foster and Bernard ended their 20-year relationship in 2008.
E! said Foster and Hedison got the rumor mill churning when they attended a Fox Studios technology seminar in the summer.