There is almost no way that Amanda can win a suit for libel in the US for people on the net referring to her as a murderer. If she could she wouldn't receive much in damages.
"There are several ways a person must go about proving that libel has taken place. For example, in the United States, the person first must prove that the statement was false. Second, that person must prove that the statement caused harm. And, third, they must prove that the statement was made without adequate research into the truthfulness of the statement. These steps are for an ordinary citizen. In the case of a celebrity or public official trying to prove libel, they must prove the first three steps, and must (in the United States) prove the statement was made with the intent to do harm, or with reckless disregard for the truth. Usually specifically referred to as "proving malice"."
She would basically have to prove that she was innocent, not not guilty. Given the widespread coverage of this case and that many people certainly are not convinced she is innocent she'd have to prove that it damaged her. As often as we may read their tripe the world has never heard of PMF or TJMK and couldn't care less what those people say.
In the uk "Allowable defenses are justification (the truth of the statement), fair comment (whether the statement was a view that a reasonable person could have held), and privilege (whether the statements were made in Parliament or in court, or whether they were fair reports of allegations in the public interest). An offer of amends is a barrier to litigation. A defamatory statement is presumed to be false unless the defendant can prove its truth. Furthermore, to collect compensatory damages, a public official or public figure must prove actual malice (knowing falsity or reckless disregard for the truth).[citation needed] A private individual must only prove negligence (not using due care) to collect compensatory damages.[citation needed] To collect punitive damages, all individuals must prove actual malice.
She is a public figure and I doubt that a court would rule that they are in reckless disregard of the truth. Once again, it would be very hard to prove damages from their tiny web sites.