She is saying "the men won't leave me alone", which to her implies not that she is a shameless, manipulative flirt, but that she is utterly & ravishingly irresistible and has to hold them at bay with a whip and chair. Catherine, who deals with her acquaintance in a more rational way, elicits a more rational response from them (in general)and interprets that response in a rational manner. She doesn't understand that Isabella is boasting, & possibly trying to make Catherine jealous that she is not so importuned.