The most important thing to remember, is that whatever her beliefs are and whatever her ethnic background is, she is a human first and she has emotions
If you contact her Wali without knowing her, she will feel that you have gone behind her back and she will be scared, you could be the coolest guy in the world, her ideal man, but it would push her away, talk to her. If she doesn't want male attention, she will tell you and then you can leave her alone, but at least you will know. Get to know the girl.
If it gets to that stage, then you can think about talking with her family, but put yourself in her shoes for a moment, what is more strange, some guy you don't know trying to talk with you, or some guy you don't know contacting your family as the first step to marrying you?