The actress has filed divorce papers seeking financial support from the 'Two and a Half Men' star - 16 months after their 2011 split - and friends believe it is because she is still hurt he allegedly cheated on her.
A source told RadarOnline: ''Demi is still really p****d off at Ashton.
''He humiliated her and then he treated her badly, which she didn't expect and it really made her mad. She basically wants to hurt him the way he hurt her, and this is the only way she knows how.''
Ashton - who is now dating 'Oz the Great and Powerful' actress Mila Kunis - filed for divorce in December 2012, but the estranged spouses have been engaged in a battle over money ever since.
It was recently claimed Demi feels she deserves a better settlement from TV's highest-paid actor Ashton, who earned a staggering $24 million in 2012 for his sitcom 'Two and a Half Men'.
The source added: ''Ashton made a lot of money after marrying Demi - a lot more than she made - but despite him becoming just as famous through her, he believes he doesn't owe her that much.''
However, the pair are said to be close to reaching a deal.