The former WWE star appeared to address Nikki and Artem's heated fallout -- which has seen both sides accuse the other of domestic violence -- sharing how the legal battle has left her eager to do something.

Brie hinted at the legal saga on the sisters' joint podcast "The Nikki & Brie Show" Friday ... where she touched on "trauma" and the urge to want to "fix" things for a struggling loved one. Yet, she acknowledged some situations you can't do anything.

Nikki wasn't on the episode, as Brie's been doing the show solo lately.

Brie continued ..."I have felt sadness in ways that maybe death could compare. I literally have lost sleep. I lay in my bed with my eyes open, and I think and I just think and think, and I think of so many different things..... But the major thing I think of is: How can I fix [things] and how can I help?"

While Brie didn't directly name Nikki or Artem ... she did emphasize the importance of "taking accountability," which appeared to echo her sister's statement following her decision to file a restraining order against the "Dancing with the Stars" pro.

TMZ broke the story ... Nikki was granted a restraining order against Artem after she detailed the alleged abuse she suffered at his hands. However, the professional dancer hit back with allegations of his own ... accusing the reality TV star of being the real aggressor in the relationship.

The update came a week after Napa County District Attorney Allison Haley announced criminal charges will not be filed against Artem ... after he was previously arrested for domestic violence back in August.

Brie appears to be siding with her twin as the drama unfolds, issuing a warning that could be interpreted as a message for her brother-in-law.

She said ... "I will say, lies will eat you up. You're always gonna get caught. No one ever runs away free without getting caught. Right? Lies will not only personally eat you up, but in the end, they'll always expose you. And you have to remember that."