Tell me if this would bother you.

[greekalumna]

A good first step might be to just ask your chapter advisor what she would recommend that you do regarding reporting the other chapter to nationals.
As for what the other chapter president told you, what would you do if she had said, "suzie was caught kissing a boy" without specifying whether that young man was African-American, Asian, Caucasian, etc: Would you relay that information to the other members of your chapter or just chalk it up to gossip? Your decision on Suzie's action should not include the race of the young man in question (this sounds like what you were going to do anyway) and really what sister hasn't been guilty of kissing someone during their college career.