Maybe. Taking advice from internet strangers is a gamble, as they aren't aware of the situation's finer details, and the only means to judge wisdom and character is by their posting style. Yet she's probably looking to vent too, and airing such private details about a fiancé to mutual friends would be a graver mistake. So at least it was anonymously posted and not some Facebook freak out. If it were me, I would have confided in my friends only, the few I trust with secrets.