3- She exhibits genuine curiosity about you.
A woman who has no romantic interest in you whatsoever will still ask you polite questions about yourself. "So where did you grow up? Where do your parents live? What kind of work do you do?"
But a woman who really likes you will show a genuine, warm, curious interest in you. She'll want to know what makes you tick. She'll want to know what's important and meaningful in your life. As you look into her eyes, you'll be able to see the wheels turning as she's trying to figure you out. That's high interest.