night owl

Translations
человек, который поздно ложится спать
She is a night owl and often stays up until 2 AM.
Она сова и часто не ложится спать до 2 часов ночи.
Definitions
A night owl is a person who tends to stay up late at night and is more active or alert during the evening and nighttime hours, often preferring to engage in activities during these times rather than in the morning.