The "toxic mom group" drama between Ashley Tisdale French, Hilary Duff and Mandy Moore has taken the internet by storm this week. "The root of the issues was that some of the women just became closer friends with each other, and Ashley started to feel left out," a source exclusively tells Us Weekly. "There were times when hangouts or get-togethers were organized at the last minute, often casual outings or quick dinners, and Ashley wasn't included. There wasn't any bad intent. Friendships naturally changed and some people bonded more than others." The source adds that French, 40, began to feel "less included" in the group, but emphasizes that the others in the group "didn't mean to exclude her." French went viral this week after she published an essay for The Cut, titled "Breaking Up With My Toxic Mom Group," on January 1. In the article, the High School Musical star described feeling excluded from her mom friends and how she ultimately left the group. Matthew Koma and More Stars React to Ashley Tisdale's Mom Group Drama "They felt like she made a bigger deal out of everything. The tension largely came from what the group saw as a clash in priorities and values," the source continues. "There were a lot of bonding moments Ashley felt she missed out on." Additionally, the source says there were "ongoing miscommunications and quiet tension" between French, Duff, 38, and Moore, 41, which "built up over time." "Hilary and Mandy are extremely close, along with Kelsey Deenihan (their makeup artist), who is in the group, and a few others, and that dynamic naturally shaped the group," the source notes. "At times, it made Ashley feel like she didn't quite fit in with the rest of the circle." As for how French is doing since leaving the group behind, a second insider says the Disney Channel alum "moved her primary residence to Malibu and feels more at peace than ever." Christian Thompson/Disneyland Resort "It has been a fresh breath of air, and she is in a much better place," the insider concludes. Us Weekly reached out to reps for French, Duff and Moore. French has yet to address the chatter about her essay, which was published after a blog post she had previously written on the subject. "There's one recent topic that has made my phone blow up like no other since I first wrote about it a few weeks ago. It's a subject that has made women DM me to say 'I feel seen' and to share their most emotional stories with me," French wrote. "It's one that has also made wannabe online sleuths try to do some investigating like they're on CSI (please, don't even try - whatever you think is true isn't even close). The topic? Mom-group drama." Ashley, who shares daughters Jupiter, 4, and Emerson, 15 months, with husband Christopher French, recalled "feeling left out," adding, "I told myself it was all in my head, and it wasn't a big deal. And yet, I could sense a growing distance between me and the other members of the group, who seemed to not even care that I wasn't around much." Christy Carlson Romano Reacts to Ashley Tisdale's Viral 'Celeb Mom Drama' Ashley said she ultimately texted the group, "This is too high school for me, and I don't want to take part in it anymore." Though Ashley did not name anyone specific in the essay, she was previously known to spend time in a mom group that included Moore, Duff and Meghan Trainor. Fans began to speculate that these celeb moms were the "mean girls" in question, but a rep for Ashley denied that the essay was about these women in a statement to TMZ. French's rep also shut down rumors that the rift was due to a difference in political views. Despite the denial, Duff's husband, Matthew Koma, fired back at the essay with an Instagram Story in which he shared a photo of himself recreating French's cover photo for The Cut. He titled his fictional essay, "A mom group tell-all through a father's eyes. When you're the most self obsessed tone deaf person on earth, other moms tend to shift focus to their actual toddlers."