Sally is very patient with her pesky little brother transitive or intransitive sentence?

The verb "is" is a linking verb.

A linking verb acts as an equals sign, the object of a linking verb restates the subject of the sentence.

Sally = patient

The object of a linking verb is called a subject complement; a noun, pronoun, or adjective that the subject is or becomes.

The subject complement "patient" is a predicate adjective.

A noun or pronoun subject complement is a predicate nominative.