a hill to die on

Translations
дело, за которое стоит бороться
For her, equal pay was a hill to die on.
Для нее равная оплата труда была делом, за которое стоит бороться.
Definitions
An issue or principle that someone feels so strongly about that they are willing to face serious consequences or make significant sacrifices for it, even if it means facing defeat or criticism. The phrase is often used to question whether a particular argument or stance is truly worth such commitment.