"Now Kelly is taking Simon's place," the person said before adding: "no wonder her marriage didn't work ... surprise she has time for her kids ... not the good old country girl we fell in love with ... it's all about Kelly being on tv ... and no one else ... no tears for her ... but for her kids."
Clarkson responded several hours later.
"Wow. Shaming a woman who has a great work ethic, is a great mom, and who steps up and fills in when a friends [sic] asks for a favor because that’s actually what “good old country girls” do," she wrote "This can’t be who you are deep down. I have more faith in your heart."
Clarkson cited “irreconcilable differences” as a cause for the divorce. Meanwhile, Blackstock, like Clarkson, is also reportedly seeking joint physical and legal custody of their children.
The divorce has yet to be finalized.
The couple was together for nearly seven years and share two young children: a daughter, River, 6, and a son, Remington, 4. Blackstock also has two children from a previous relationship.