Answer:
"Fain" means "gladly" or "willingly." Juliet is saying that she wants to dwell on form (the importance of names and titles) and deny what she has just spoken (her desire for Romeo to give up his name and be with her). However, she adds "farewell, compliment," which means that she is saying goodbye to the idea of paying compliments and saying things just for the sake of social convention or politeness.
In other words, Juliet is torn between her desire to be with Romeo and the social conventions and expectations that are keeping them apart. She would like to ignore these conventions and deny the importance of names and titles, but she knows that she cannot. By saying "farewell, compliment," she is acknowledging that she must say goodbye to these polite fictions and face the reality of the situation.
Step-by-step explanation:
After Juliet asks Romeo to deny his name and be with her, she speaks the lines you are asking about.