I am sure she thought this through much more thoroughly than the last time because no one wants to be hurt twice. I am certain she, who made the choice to marry the fellow, is aware of the rumors circulating about him. However, if you are so afraid that she may not have been introduced to this information, and you feel it’s so crucial that she know, call her Rav and have him speak to her. This is not your job! If this caring is truly altruistic for HER benefit, you can call her family’s rav and trust him to decide if he should pass the information forward.
Anyway, she will likely think you are a stalker and a creep if you approach her yourself.