эгоисткой

(as) an egoist, (as) a selfish person

→ эгоистка
эгоистк female egoist + ой singular instrumental feminine
noun · feminine singular · instrumental Rare #43,048
(as) an egoist, (as) a selfish person Instrumental singular feminine; used after verbs like "быть" (to be) or with meanings like "as" / "with".
RU: Она была эгоисткой и думала только о себе.
EN: She was an egoist and thought only about herself.
Declension of эгоистка
SingularPlural
Nominative эгоистка
Instrumental эгоисткой

Хасинта, дочка, не будь такой эгоисткой.

Jacinta, daughter, don't be so selfish.

— Боль и слава (2019)