Friends who partied with and knew singer D4vd were under the impression Celeste Rivas was his girlfriend, and were shocked when news came out Celeste was only 14.

Sources who party in the L.A. music scene tell TMZ ... they saw D4vd and Celeste at parties and hangouts ... and it appeared to them they were a couple.

We're told some of them were under the impression she was a student at USC. The friends believed Celeste was around 19 years old and presented herself as such.

TMZ broke the story ... law enforcement sources say Celeste had multiple fake IDs, which allowed her to pass herself off as an adult.

The people who are now buzzing about what they saw tell TMZ ... one of the reasons they thought she was over 18 was because she was hanging out at places that had age restrictions.

Another thing we're told ... D4vd's contemporaries who were at these parties and hangouts were shocked there was any remote connection between D4vd and Celeste's death -- something that has not been established as far as we know -- because his demeanor was "super shy, soft spoken and gentle."

As we reported, law enforcement says Celeste ran away multiple times and came from a "troubled home."

Before law enforcement identified Celeste as the victim found in D4vd's Tesla trunk, her mom told TMZ she had been dating someone named David.