Louella Michie’s father, Holby City actor John Michie, said his daughter appeared to have taken an “illegal substance” before her death.
Her body was found in woodland on the edge of the Lulworth site on Monday.
A festival spokeswoman said the event had a “zero tolerance” to the use of drugs, with searches and passive drugs dogs at all entrances.
Bestival, which is organised by DJ Rob da Bank and his wife Josie, said its team had worked closely with its security contractor and Dorset Police to “deliver a safe event” at the Lulworth Estate.
A statement said “amnesty bins” were available on the approaches to entrances for people to get rid of any drugs.
It said the search operation at the entrances was “well resourced”, and anyone who “failed” or refused to be searched was refused entry.
People found to have quantities of illegal drugs for supply were detained and handed over to police, the statement said.
The festival spokeswoman said the team was “devastated” by Miss Michie’s death.
Posting a thank you message on Instagram to festival-goers and the event’s staff, Rob da Bank said: “My thoughts remain with the family and friends of Louella.”
In a statement about the policing of the event, Ch Insp Chris Weeks said the force and festival had worked closely together.
“Event security used a number of tactics to identify drug use, including sniffer dogs at entrance points,” he said.
“Police officers were also proactively patrolling the site throughout the whole event.”
The force said 88 crimes were reported during the event with 36 arrests made, 27 of which were drug-related.
Following an inconclusive post-mortem examination, further tests are being carried out so see if there were any substances in Ms Michie’s system.
Police arrested her friend Ceon Broughton, 28, on suspicion of her murder and supplying a class A drug on Monday.
Mr Broughton, from London, was released under investigation on Tuesday.
Bestival was first held in 2004 at Robin Hill on the Isle of Wight, but the four-day annual event was held at Lulworth Estate for the first time this year.