Tanesha Melbourne-Blake was fatally shot as she danced and socialised with friends in Tottenham on the evening of Easter Monday, 2 April 2018.
Jurors were told the killing came at the peak of tit-for-tat violence between two neighbouring gangs in north London and an incident the day before when La Croix was beaten up. The court heard Tanesha did not associate with gangs and may not have been the intended target.
La Croix, from Hackney and also known as Bobby Slater, was cleared of murder and possession of a firearm with intent to endanger life following a retrial. The jury deliberated for 13 hours and 34 minutes.
Co-accused Michael Clarke, from Luton, faced a retrial. His jury was discharged last week after failing to reach a verdict. On Friday, the prosecution offered no evidence, and he was formally acquitted of the same charges.
Judge Mark Dennis KC lifted reporting restrictions following the conclusion of proceedings. Tanesha's mother left the court in tears after the verdicts in May.
A month after the shooting, a street cleaner recovered the gun wrapped in a towel dumped in a grassy area. Examination of a bullet found it was fired from the same weapon used in the fatal shooting of Joseph Williams-Torres, 20, in Walthamstow in March 2018.
Her boyfriend told the court he had no idea why the incident happened, and that the couple did not associate with gangs or have issues with anyone.