Kristin Cavallari was reportedly ''blindsided'' by Jay Cutler's filing for divorce.

The 33-year-old reality star knew ''that their marriage has been over'' for some time but wasn't expecting her estranged husband to lodge paperwork to legally end their union last week and the sudden move has damaged their ''amicable'' negotiations.

A source told E! News: ''She had hoped they could work things out more amicably and they were off to a good start before Jay pulled the trigger.''

In Jay's filing, he stated he was the ''available at home parent and the primary caretaker of the parties' minor children'', despite reportedly having previously agreed to equal care of their brood, Camden, seven, Jaxon, five, and Saylor, four, and so Kristen was further ''caught off guard''.

The source added: ''His filing was basically trying to take her out of the equation so she had to respond strongly. She's not going to be taken out of the equation when it comes to her children.''

Another source added: ''Jay was playing for the NFL a majority of their marriage, for him to call himself the primary caregiver just because he is retired and she is working is not accurate.''

The 'Very Cavallari' star is now working to seek full custody of the children because she ''feels she can raise the kids in the safest environment.''

Prior to Jay's divorce petition, he and Kristin had been ''staying in the house three days on and three days off'' so the kids could stay in their home but now the former couple are ''on edge'' and both are living in ''separate parts'' of their Nashville abode.

In her divorce filing, the Uncommon James owner accused the 36-year-old NFL player of ''inappropriate marital conduct'', and also cited ''irreconcilable differences'' as a reason for ending their seven-year marriage.

She alleged Jay is ''guilty of such inappropriate marital conduct as renders further cohabitation unsafe and improper''.

According to the documents, Kristin listed their date of separation as April 7, whilst in his own papers, Jay dated their split as April 21.