Liberty Ross reportedly filed for divorce as she realised she couldn't get over the "public embarrassment" Rupert Sanders inflicted on her.
British film director Sanders, 42, had an affair with Kristen Stewart, 22, last year, after they met on the set of Snow White and the Huntsman.
Although Ross tried hard to work on her marriage and even attended counselling, last week she filed for divorce. It's been claimed the model finally realised she couldn't move past the betrayal.
"For the sake of her own happiness, she had to finally go through with the divorce," an insider told RadarOnline.com.
"No matter how hard she tried, she just couldn't forgive Rupert for cheating on her with Kristen - especially since it was something that caused such public embarrassment. The images of Rupert and Kristen together making out were out there for everyone to see. Liberty just couldn't get those pictures out of her head."
Ross and Sanders have two children together, which apparently made her decision even tougher.
Although she found the thought of disrupting the kids' lives difficult, the star apparently realised she needs to move on after "months of painful soul searching".
The model filed documents to end her marriage on Friday and requested joint custody of her children with Rupert. She also asked for spousal support, while Sanders lodged papers on the same day and also asked for joint custody.
When the pictures of Stewart and Sanders together were leaked, the actress released a statement apologising to her boyfriend and Twilight co-star Robert Pattinson.
The young couple were thought to have worked through their issues and united to promote the final instalment of the vampire franchise Breaking Dawn - Part 2 at the end of last year.
However, new reports suggest they have gone their separate ways after Pattinson realised he could not get past the affair.
- Cover Media