According to her flatmate, Evgenia Sviridenko, 24, had been looking at her social media page on VKontakte - the Russian version of Facebook - when the accident happened.
Speaking from the apartment the women shared in Moscow, Yaroslav Dubinina, 23, said: "I noticed that she had been gone a while, and when I couldn't raise her I opened the door and saw her floating on the water looking pale.
"I saw her phone which was on charge at the bottom of the bath. Her body was still shaking from the shock."
Police are investigating why the charger did not cut out and would not reveal whether it was a licensed Apple product.
Evgenia's death comes days after a 16-year-old girl died in Russia's Bashkortostan Republic after taking her charging phone into the bathroom as she was taking a shower.
In August, Chinese media reported that a teenager was electrocuted by her iPhone after it was plugged into an unofficial charger.
Wu Weyuan, an 18-year-old student from Korla was discovered by her sister, who noticed a burning smell when she came home from work.
Apple has previously released statements on its website warning of the dangers of using unofficial chargers.
In October, a man claimed an iPhone 6 bent in his pocket and caught fire, leaving him with a second degree burn.
Phillip Lechter was visiting the University of Arizona when the incident happened and said a passer-by had to throw water on his trousers to put out the blaze.