Warning for single women in Roc?

Is there a subreddit or other platform option for warning women against predators? My friends ex did quite a number on her with psychological and sexual abuse and thankfully she has finally escaped. She'd like to warn local women because he is a "serial monogamist" and she doesn't want others to go through the hell she has. This is obviously not the group for it, but it's important information that should be in the right hands.