"He and I have been friends for a really long time, for like 17 years and it just grew from friendship to more than that," the iconic songstress told ET's Courtney Tezeno at the premier of The Forgiven at the Directors Guild of America in Los Angeles on Wednesday.
"So you gotta keep your friends close," she added. "You never know what can happen."
Braxton confirmed that she and Birdman are engaged last month when she posted a promo for her reality show, Braxton Family Values, in which she reveals the news to her sisters.
Now, with wedding bells chiming on the horizon, Braxton says she's already making plans for her big day.
"The cake is important… and the dress," Braxton, 50, shared. "I'm particular about the dress… I have to find something that's appropriate but sexy at the same time."
Braxton and Birdman (whose real name is Bryan Christopher Williams), began dating in May 2016 and made their first public appearance together at the BET Awards later that year. Braxton was previously married to musician Keri Lewis for 12 years. The couple, who divorced in 2013, share two sons -- Denim, 16, and Diezel, 14.
"I haven't been happy in a long time outside of work. Work brings me extreme happiness. When I'm on stage and I'm performing, that's the only time that I get those butterflies and I feel totally happy with my life," she shared. "A romantic relationship? I haven't had time for that -- I should say, I chose not to make time for it, but it's right here in front of my face: happiness."
Check out the video below to hear more.
The Forgiven, which features music by Braxton, hits theaters March 9.