Beauty queen Baylee Curran told the LA Times Mr Brown had pointed the gun at her face after she had been admiring his friend's jewellery.
Mr Brown came out of his home after a stand-off with police on Tuesday.
The singer has several convictions for violence, including a 2009 assault on his then girlfriend, pop star Rihanna.
Police went to Mr Brown's home following the emergency call early on Tuesday from Ms Curran, who by that time had left the property.
Ms Curran told the LA Times that she and a friend had gone to Mr Brown's house with a business associate on Monday evening.
She said she had been admiring the diamond necklace of a man who had been showing off his jewellery when the man got angry and told her to back away.
That is when she says Mr Brown pulled out a gun, pointed it at her face and told her to get out.
"If somebody put a gun to your head, what would you do? Call the police," Ms Curran said on her Instagram account, AFP news agency reported.
Police said about half a dozen people had been escorted out of the residence after the stand-off ended and would be interviewed.
Before emerging from his home, Mr Brown posted videos online criticising the police action.
"When you get the warrant for whatever you need to do, you're going to walk right up in here and you're going to see nothing, you idiots," he said in one Instagramvideo, posted to 30m followers.
In another, Mr Brown also voiced support for the Black Lives Matter movement against police brutality, saying: "You're all the worst gang in the world, the police."