It's 'useless' trying to change her mind. = It's 'useless' to try to change her mind.
Drugs are 'useless' in treating the condition.
I made a 'useless' attempt at fixing the leak.
(..) - I don't know who he is. His stuff comes in the mail. - Liar! - I swear. - He's the one who can bring me to him. - I don't know who he is. - You are useless. Set him down, tough guy. - Speak of the devil. - Spiderman! I knew you two were in this together. Hey, kiddo, let Mom and Dad (..)2002 Spider-Man