The Lady camelast night. The underlined word is a noun phrase. But here in this sentence it is being used as a/an:

The Lady came last night. The underlined word is a noun phrase. But here in this sentence it is being used as an Adverb. 

A noun phrase consists of a noun or pronoun, which is called the head, and any dependent words before or after the head. Dependent words give specific information about the head.

Nouns and noun phrases can act as adverbials – that is, they can modify or add information to a verb. When noun phrases act in such a role, they describe time, place, quantity, or manner. Ex: He arrived this morning.

Source: British Council Learning website