。
She doesn't care about her appearance.
Literal
She [topic-は] attire [object-を] doesn't-care-about.
身なり (みなり) refers specifically to personal appearance through clothing and grooming — how someone presents themselves visually. The verb かまう (構う) means 'to mind, to care about,' and in negative form かまわない becomes 'doesn't care, doesn't mind.' The construction 身なりをかまわない is a set expression for someone who pays little attention to how they look, implying neglect rather than deliberate style choices.