In late September, the Two and a Half Men star was reportedly seen partying with a mystery blonde named Sara Leal.
Leal has since claimed that Kutcher seduced her, telling her that he was "separated" from Moore.
Moore is now not eating properly due to stress from the alleged affair, according to Us Weekly.
"She is superskinny, and it's hard to look at," a source claimed. "She's very upset, and hasn't been eating. It's taking a toll."
Kutcher and Moore were spotted camping over the weekend near Santa Barbara with a Kabbalah instructor.
Moore was reported to have consulted a divorce lawyer last week following allegations of Kutcher's infidelity.