Helen's physical appearance does not make her stand out, but her high spirits and (select a word) demeanor make her captivating and appealing.

I believe the answer is 'pert demeanor'

Pert demeanor could also be use in determining the interest of other people around her. in this case it include traditional roles for women (large breast, wide hips pretty face) and traditional roles for men (strong, well muscled, financially independent, funny, etc)