"I know that teenagers are just hard to deal with at that age ... but COME ON, there's being rude then there's being HATEFUL ... they would visit me, walk in the door, go straight to their room and lock the door !!!" she wrote. "I'm like why come visit me if they don't even visit me !!! But I never said that because I have to be kind !!!"
She concluded her Instagram post by writing, "It breaks my heart because it seems to me that these days, cruelty does in fact win, although it's not about winning or losing !!! But I can't process how I dedicated 20 years of my life to those kids ... everything was about them !!! For them to knock the breath out of me."
In response to Spears' post, Federline's lawyer, Mark Vincent Kaplan, told TMZ the kids have chosen to keep their distance from the singer of their own accord.
Later on Wednesday, Federline, 44, posted a series of edited videos from four years ago of the singer appearing to argue with the boys to his Instagram account. In the caption, he said that he and the boys decided "as a family" to share the clips and that "the lies have to stop."
Lester Cohen/WireImage; Mindy Small/FilmMagic Britney Spears and Kevin Federline
On Thursday, Spears' lawyer Mathew Rosengart hit back in a statement to PEOPLE and asked Federline to respect his ex's privacy.
"Britney has faithfully supported her children and she loves them dearly. Whether he realizes it or not, Mr. Federline has not only violated the privacy and dignity of the mother of his children, he has undermined his own children, whose privacy he should protect," the statement read.
He continued, "Putting aside his ITV interview, Mr. Federline's ill-advised decision to post an old video of his 11 and 12-year-old children was cruel, bottom-of-the-barrel stuff. It was abhorrent. In addition to demeaning himself and violating societal norms, he has now also created various legal issues for himself including, but not limited to, implicating cyber-harassment and cyber-bullying statutes, among other things."
He later added, "We are working with Instagram to ensure that Mr. Federline adheres to its rules and we are exploring all appropriate relief against him. In the meantime, as Britney herself poignantly said, whatever is occurring between her and her boys should remain private. We urge Mr. Federline to act with a measure of grace and decency and to cease from publicly discussing private matters, which benefits no one."
Insisting that the teens love their mother, Federline told the publication, "The boys have decided they are not seeing her right now. It's been a few months since they've seen her. They made the decision not to go to her wedding."
Federline also said he has had a hard time explaining Spears' decision to post nude and nearly nude photos online to his two sons. "'Look, maybe that's just another way she tries to express herself,' " Federline explained as to what he has said to his sons, he told The Daily Mail. "But that doesn't take away from the fact of what it does to them. It's tough. I can't imagine how it feels to be a teenager having to go to high school."
Britney Spears Instagram Preston, Britney Spears and Jayden
Spears reacted to Federline's statements in an Instagram Story post on Saturday evening, where she wrote, "It saddens me to hear that my ex-husband has decided to discuss the relationship between me and my children."
"As we all know, raising teenage boys is never easy for anyone. It concerns me the reason is based on my Instagram. It was LONG before Instagram," she continued, referencing Federline's issue with her social media posts.
Noting that she "gave them everything," the "Me Against the Music" singer added, "Only one word: HURTFUL."
Spears' husband Sam Asghari, 28, also chimed in to express support for Spears. In an Instagram Story post of his own, he spoke out about Spears' social media posts and how the images and videos she shares online are more "modest" than those shared within advertisements and by others.