Trina Braxton is on cloud nine after her engagement to Von Scales -- but her sister, Tamar, isn't having it.
In ET's exclusive sneak peek of Thursday's episode of Braxton Family Values, Tamar freaks out and storms off after Trina gets engaged at Tamar's birthday dinner. Despite Toni's attempts to have her "grow up" and rejoin the table, Tamar holds her ground, maintaining that it was disrespectful for Von and Trina to steal the spotlight.
"Will you do me the honor of being my wife?" Von begins in the clip, emotionally looking into Trina's eyes at the dinner table.
"I love you very much, and nothing would please me more than to be your wife," she replies, visibly shocked by the proposal. "So my answer is yes!"
The family celebrates -- except for Tamar. "It's at my birthday though -- like what the f**k is going on?" she yells from the opposite side of the table, eventually giving Trina and Von congratulatory kisses and then storming away.
Toni follows her, insisting that her behavior isn't a "good look." But the damage has been done, according to Tamar.
"Ain't nobody's proposal on my f**king birthday!" she yells. "I'm done. Done and done!"
Trina opened up about her engagement while speaking with ET earlier this year, revealing that Von's proposal during the family's getaway to California wine country (a trip to celebrate Traci and Tamar's birthdays) couldn't have been more unexpected.
"We were in Napa Valley, you know, all the girls were together, we were filming and he just kinda, like, plopped the box on the table and just… I lost it, totally, fully and completely," she recalled.
After the proposal, an angered Tamar went live on Instagram to vent her frustrations. "I got one card! Like we work in the cubicle side by side together at Sav-On. I’m just saying, like, the s**t going on, this is not a birthday celebration for me! This is some straight foul f**king s**t that nobody put no thought into … and if I don’t have the attention from my sisters, who the f**k am I supposed to get it from?!"
See more on the drama in the video below.
Braxton Family Values airs Thursdays at 9 p.m. ET/PT on WE tv.