Possible Clues:

• She's of good appearance but not of good behaviour
• She's so good-looking, but rather naughty
• Naughty but nice-looking
• Lovely to look at but not nice to know
• Looks all right, but is rather high (6, 3)
• Nice to look at, but not so nice to know
• Are good looks not so good?
• Nice to look at, but not a very good girl
• Not so good to look so good
• Though good-looking, she's a bit of no-good