Locklear's decision to seek help comes on the heels of a February 25 arrest at her California home, for which she was booked on suspicion of felony domestic violence and three counts of misdemeanor battery on a police officer.
"Ava begged her mom to go to rehab", the source says.
On Tuesday, police reportedly searched Locklear's home looking for the gun. She was also arrested on three counts of misdemeanor battery of a peace officer.
Still, the source said Locklear isn't totally convinced she has a problem, and instead thinks the whole mess is a "mistake" to be blamed on her brother and boyfriend Chris Heisser.
Detectives from The City of Thousand Oaks Police Department executed a search at Locklear's home on Tuesday, but were unable to locate and seize the firearm, which is registered in her name, according to KABC-TV, Channel 7, in Los Angeles.More news: Promoter in failed Bahamas music festival pleads guilty
Locklear's first court appearance is scheduled for March 13, while Heisser's DUI hearing is set for April.
Locklear told deputies she would shoot them if they ever came to her house again, investigators said. "She posted $20,000 bail and was released".
She also shared a photo of her with Heisser, captioned "So grateful for you".
He added: "I don't know when she got the handgun, but I do know that yes, she did make that statement to the police the night that she was arrested".
A rep and an attorney for Locklear did not immediately return requests for comment.