。
She is very clever.
Literal
She [topic-は] very clever is.
利口 is a na-adjective for 'sharp, quick-witted, shrewd,' often with the flavor of practical cleverness rather than pure intelligence. It's also commonly used of well-behaved children and pets — calling a dog 利口 is a compliment about its training or smarts. For raw academic intelligence you'd hear 賢い or 頭がいい more readily; 利口 leans toward streetsmart and adaptive.