Sources told American tabloid The National Enquirer that the two have come to blows over DeGeneres' friendships with other women.
Portia was recently left furious when she caught the chat show host texting "X-Files" star Anderson, reports showbizspy.com.
"Ellen and Gillian have been close friends for years and set tongues wagging when they were caught sharing a steamy lip lock in 2000," said a source.
"Ellen has always had a major crush on Gillian, but she's sworn up and down to Portia nothing happened between them. But Portia doesn't believe her.
"Ellen and Gillian adore each other. Portia's not too happy about it and wants them to stop communicating. She's afraid Ellen will be tempted to stray, even though the funnygal insists that would never happen," the source added.