D4vd's Former Friend Aysia Collins Says He's Psychopath Who Betrayed His Circle

D4vd's former friend Aysia Collins is slamming the alleged killer and firing back at folks online who claim she's cosplaying and mocking Celeste Rivas.

Aysia -- who ran in the same group as the singer and the slain teenager -- shared a screenshot of a DM she received ... where a friend is asking her about a comment on a since-deleted Aysia Instagram post. The comment says, "she cosplayed and mocked a dead missing little girl your weird."

She told her friend people think she's cosplaying Celeste because she has curly hair and used to hang with D4vd ... and then she went off on D4vd and the person who left the comment.

Aysia says folks need to use their brains when talking about Celeste's case ... because it's not something to "spew bulls***" about.

She says she hasn't wanted to respond to the cosplay allegations ... but she's doing so now because "to say I cosplayed as a child just because we are the same skin tone and have curls is insane work."

Aysia then clarifies she and D4vd are no longer friends ... calling him a "psychopath" who "lied and betrayed everyone around him."

As you know ... D4vd was arrested back in April -- months after Celeste's mutilated body was found in the trunk of his Tesla in the Hollywood Hills.

D4vd's since been charged with one count each of murder, continuous sexual abuse of a child under the age of 14 and unlawful mutilation of human remains