Kutcher, who is now romantically involved with Mila Kunis, was found cheating on Moore on their sixth wedding anniversary in 2011.
"Demi wants nothing more than to be able to move forward with her life, but she's still really, really upset about Ashton and Mila, it eats her up every time she hears about them or see pictures of them together," radaronline.com quoted a source as saying.
"She's doing everything she can right now to live her life to the fullest, but it's hard to move on because she still has feelings for Ashton and hasn't found a suitable distraction just yet," the source added.
The 50-year-old actress was recently rumoured to be dating British comedian Russell Brand, but the latter denied it.
Pics: Prabhas, Tamannaah Bhatia at 'Baahubali 2' first look launch at MAMI
'Ae Dil Hai Mushkil' photos: Aishwarya, Anushka, Karan get candid at MAMI
Photos: Huma Qureshi, Neha Dhupia and other celebs at MAMI
Photos: Amy Jackson, Daisy Shah at Mumbai airport
Photos: Sridevi, Irrfan and other celebs at 'Mughal-e-Azam' screening