Oh dear.
What an awful situation.
HoneyDip05, I know this circumstance does not sit well with you at all and you said that you are having a hard time letting it go. I am certain that you understand that this is about *her* integrity, not yours. At the end of the day, you rightfully earned your place in your sisterhood and she did not. I know it seems unfair and disrespectful and you want justice for your organization. *She* is the one who has to look at herself in the mirror every morning and *she* knows what she did. Even if it doesn't sit well with your soul, know that you are on this side of right and the situation is what it is at this point.
I'm not an NPHC member; so, it's not my place to comment on if you should try to report her. I agree with Sen that that you should at least unfriend her. Since you had the disagreement with her over messages, if you did report her, she would most certainly believe it was you who did it. Such a tough call.