For what does Curley’s wife yell at Lennie?

Curley's wife yells because Curley messes up and then pulls her hair.

Look out, now, you’ll muss it.” And then she cried angrily,“You stop it now, you’ll mess it all up.” She jerked her head sideways, and Lennie’s fingers closed on her hair and hung on. “Let go,” she cried. “You let go!”