которую я когда-либо

that I have ever

→ который
phrase Rare #32,823
that I have ever Used with a feminine noun to mean “that I have ever...” in superlative expressions. The verb is usually in the past tense, and когда-либо means “ever.”
RU: Это самая интересная книга, которую я когда-либо читала.
EN: This is the most interesting book I have ever read.