Just traces of it. It is not like she was drunk or high on drugs. A completely clean person without a life vest likely would have drowned, too. There were dangerous currents in that lake.

https://abc7ny.com/naya-rivera-glee-toxicology-report-lake/6419478/
https://www.hollywoodreporter.com/news/general-news/autopsy-report-indicates-naya-rivera-called-for-help-as-she-drowned-4059125/

>It revealed that the 33-year-old Rivera had previous problems with vertigo, had a recent sinus infection, and had a small amount of prescribed amphetamines in her system, but did not identify physical conditions or drugs as factors in her death.

>Toxicology tests also showed she had small, therapeutic amounts of the anti-anxiety drug diazepam and the appetite suppressant phentermine in her system.

https://www.latimes.com/california/story/2020-09-11/naya-rivera-autopsy

>The autopsy report included the medical examiner’s earlier determination that the drowning was accidental and added the new information that she had a low level of amphetamine and diazepam, caffeine and a blood-alcohol level of 0.016%.

>The autopsy did not say whether the medication and alcohol played a role in her death. Her blood-alcohol level was five times lower than the legal limit for drunken driving in California, 0.08%.

That wasn't why she died though.

He was a beloved pet and reached the age of 19. He died in 2017.