Look! Her hands (to be) dirty. She (to work) in the

 Look! Her hands are dirty. She has been working in the garden.

The first sentence is in Present Indefinite. Are is the present form of the verb to be. The second sentence is in Present Perfect Continuous. Present Perfect Continuous is formed with two auxiliaries to have and to be. We add the suffix ing to the verb.

Subject + have / has + been + verb + ing.

Negative Subject + have / has + not+ been + verb + ing.

She has not been working in the garden.

 Interrogative Have / has + subject+ been + verb + ing.

Has she been working in the garden?