This is the 158th most frequent Russian word.
ей
The Russian word "ей" means "to her" or "for her" (dative case of "она").
The word 'ей' acts as a dative pronoun referring to 'her', indicating the indirect object of the action.
Я дал ей свой телефон.
I gave her my phone.
Here, 'ей' is used as a dative case pronoun indicating the person experiencing the condition 'feels cold'.
Ей холодно в этом помещении.
She feels cold in this room.
In this case, 'ей' functions as a dative pronoun referring to 'her', being the recipient of the phone call.