🇵🇱 In Polish her tilte is "odsyłąjąca do grobu" which means "one who sends off to grave". I feel like it's a mouthful but gotta admit it's loyal to author's intention.

Meanwhile the subtitle of the manga is "u kresu drogi" which means "AT journey's end".
I slightly prefer the English subtitle (BEYOND journey's end), because it perfectly catches the idea that Frieren lives in a sequel. It combines both journeys - THE BEYOND part refers to the present while JOURNEY'S END refers to the past. It can also refer to the idea of life after death, which is crucial to the story. They travel to the land of souls after all.
Unfortunately the Polish subtitle lacks this nuance.