إِنَّهَا زَيْنَبُ قَائِمَةٌ.
Meaning: The matter is that Zaynab is standing.
Parsing: inna is the accusative-governing particle; -hā is the feminine narrative pronoun as its noun in the accusative position; Zaynab is the subject of the inner nominal clause; qāʾimatun is its nominative predicate; the inner clause as a whole is the predicate of inna.
The inner sentence, not just the word Zaynab, serves as the predicate.