"This is her day!"
Translation:זה היום שלה!
It's not unexpected but interesting that there is no את in nominal sentences, because for definite object with יש then את is present and technically יש is not a verb so that is a nominal sentence, too. I guess that יש acts like a verb even though it's a particle, while verbless (nominal) sentences such as we have here only have subject and predicate but no object, hence no את. Although hard to read because it transliterates the Hebrew, the classic study for ancient Hebrew nominal sentences in English is Francis I. Andersen, The Hebrew Verbless Clause in the Pentateuch (1970). It's interesting that את as object marker is less common in Qumran Hebrew and rabbinic Hebrew, but modern Hebrew revived the classical Hebrew usage to some extent. But I digress, since את is not needed here. I'm rambling about this topic because there's a discussion of יש את (that is, יש + definite object marker את) that discusses why את occurs in that context.