Dear Volodymyr,
Though Eastern Catholics no doubt already venerated St. Euphrosyne for as long as the Orthodox have, there was no FORMAL recognition of her sainthood in the Catholic Church until the 20th century. As someone noted, sainthood in the Orthodox Church is normally “down-up,” while in the Catholic Church it is officially “up-down.” In this case, I think the FORMAL recognition of her sainthood was just that, a formality. I do not doubt that JPII of blessed memory who pronounced the formal canonization, himself a Slavic Christian, already had a private veneration of her.
God bless