Rimes had a very public affair Eddie Cibrian when he was married to Glanville, and Rimes and Cibrian both divorced their then-spouses to marry each other.
Cibrian and Glanville had two sons together, and those boys are now Rimes' stepchildren. She tweeted about Glanville's children - Mason, 8, and Jake, 5 - on Friday and Glanville, who stars in "The Real Housewives of Beverly Hills," didn't appear to like it.
On Nov. 30 Rimes tweeted: "Flying out with my boys in a few hrs. Love that it's a family tour weekend. It's always more fun when they are with me."
On Saturday, Glanville, 40, tweeted to her more than 157,000 Twitter followers: "Someone is trying 2 get under my skin by calling MY children "her boys"Sooo transparent!They R MY boys, Eddie Boys and ur step-sons… 4 now"
As the weekend continued Glanville continued to tweet, ""Im taking a moment from twitter to breathe and punch some pillows."
When Glanville follower @FromFL responded to her tweet with this: "@BrandiGlanville deep breaths! Until she's a mother herself she won't grasp that concept. Hang in there!" Glanville replied: "@FromFL she needs a baby stat!)"
But that wasn't all. Glanville also tweeted this on Saturday: "a friend just sent me a video of MY 5 yr old riding his bike on a busy st without his training wheels & without a F*****G Helmet"
Another follower tweeted the "Housewives" star and said she hated Rimes, and Glanville took it even further with her reply: "I dont hate her I feel sorry for her but if she hurts my kids I will cut a b**ch or probably something worse."
It's not the first time Glanville has expressed such strong feelings about Rimes. In an interview with Radar Online, Glanville said she thought she was going to "physically hurt" Rimes when the singer turned up at her sons' soccer games.
"I remember walking up to soccer practice and there she was with my baby in her lap," Glanville said. "My blood was boiling, and I thought I was going to kill her. I really thought I was going to physically hurt her. … She was sitting in my soccer chair, under my tent. She's got my kid on her lap, and she's with my husband, and that was that little moment of total irrational fury."
Rimes has been tweeting about being a stepmother, and has asked her followers who are stepmothers to add the hashtag # TwitterStepmoms to their profiles.
Rimes, 30, hit country stardom when she was a young teen and later became a crossover pop star. She recently went to a rehab program to cope with anxiety and stress.