The latest round of sniping comes after a weekend incident involving Cibrian and Glanville's two sons.
We'll let LeAnn explain:
"Flew home for 5 hrs to see Eddie & the lil one's and ended up in the ER!" Rimes tweeted on Saturday. "Everybody's fine, just a minor kiddo accident. Boys will be boys!"
And mothers will be mothers—which means they don't want to be the last ones to hear about their kids' forays into the emergency room, which is how Glanville says she came to find out about 7-year-old Mason's injury.
"All I know is I didn't get a phone call," Glanville told E! News. "Poor choice. Bad parenting."
As for how the chin-splitting injury occurred, the concerned mom said, "I don't know how exactly it happened, but Mason told me LeAnn had oil on her hardwood floors and he fell."
"Eddie didn't bother to call me and I showed up to Mason's soccer game that day only to get a text from Eddie afterwards saying Mason wouldn't be playing since he was in the ER all morning."
The blame for that, according to Glanville, is Rimes.
"I'm disappointed in their decision. I'm the mother of these two boys and if we're going to coparent, we have to do that together. It's not call me after."
And while Glanville previously told E! News she was becoming increasingly concerned about her children's safety at Casa Rimes, she admits that may have been a bit of an overblown reaction.
"[The boys] are not in danger," she said. "The only thing that's in danger is our coparenting relationship if [LeAnn] keeps involving herself and doesn't allow [Eddie] to call me."
Incidentally, this isn't the first time one of the children has contracted a boo-boo under LeAnn's care: youngest son, 3-year-old Jake, also sustained an injury while playing on the singer's tour bus.
"The last time they had the boys, Jake ended up getting seven stitches," she said. "I had to call in a plastic surgeon to stitch up Jake's forehead."
We're guessing the phrase "boys will be boys" was no more consoling the first time around, either.
For her part, Rimes' rep told E! News that the most recent accident was nothing more than "a minor slip" and that "Eddie and LeAnn were with him the whole time, and he is all smiles now."
Which is more or less what she tweeted immediately after the incident.
Everyone except Glanville, whom Rimes perhaps suspected would not be pleased about the seemingly harmless accident.
She spent the next two days both defending herself against followers who seemed to take issue with her newfound surrogate parenting and her relationship with Brandi.
"To be really honest, it's not her place to tell me how to be," Rimes wrote. "I respect her as their mom, but she has to understand they're in my life. I can talk about my life just like she can take about her's.
"Just so you know, she has never spoken to me. This IS my life too and they are in it 50% of the time…I've stepped into a very tough, but rewarding role…I treat those boys like they are my own because that's how I love."
And, from the sounds of it, she plans to go on doing more of the same for awhile to come.
"Not an easy situation," she went on, "but I know there are many women out there who are experiencing some if the same challenges as me. I have hope for a peaceful future."
Tune in to E! News tonight at 7 and 11:30 for the latest on Glanville vs. Rimes.
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