"엉뚱하다" => wacky and unpredictable in character. (usually not viewed negatively) "똑 부러지다" => curt, sharp and decisive. Not vague or dragging things out. "level-headed" and "firm". 똑 부러지다 comes from 똑 (or 딱 - sound, shape of something snapping) + 부러지다 (snap, break in two). So it literally means something is hard and clear cut, and tends to break rather than bend or change forms. When it comes to people's character, it suggests a positive quality, like straightforward, honest and unequivocating. "똑 부러지지만 엉뚱한 매력도 가지고 있는 여자" I think your translation is as good as any. Another way might be "A woman straightforward and firm in manner yet who still has unexpectedly wacky charms"