The friend added, "I think Kym has known for a long time, in her heart of hearts, that things weren't going to work out.
"The bust-up at their house a few weeks ago was the final straw. It left Kym frightened for her safety. She can't live like that."
The star, 37, was said to be especially worried about her children; the couple's two-year-old daughter Polly, and her son David, 18, and daughter Emily, 15, from a previous relationship.
"She desperately tried to make the marriage work for the sake of their daughter, but it's obvious that things can't continue. Kym's only focus now is her children. To say she is devastated is an understatement."
Kym’s decision to end her marriage comes amid allegations she had a five-month fling with her Coronation Street co-star Oliver Mellor.
According to the Sun, the pair got together just five months after Kym’s marriage to Jamie. "They both knew it was wrong because Kym had only just got married – but they just couldn't resist each other," an insider revealed. "The chemistry between them was just too strong."
The affair is said to have begun around the time of the arson attack on the Rovers Return, when Oliver's character Dr Matt Carter took part in a striptease. At the time Jamie was away in America.
"Oliver definitely caught Kim's eye during the striptease – they were eyeing each other up all night during those scenes.
"The chemistry was building and building. Kym is one of the sexiest women on TV and Oliver was loving every minute of it."
Kym is now said to be staying with a friend after leaving the marital home in Worsley, Greater Manchester.
EastEnders actor Jamie, 33, is currently staying in London. At the weekend, he sent a message to Oliver on Twitter that read, "You need to come and see me". He deleted the tweet 10 minutes later, but not before it was seen by his followers.