But what makes it not protected speech? It’s not illegal to lie. I think her husband is very wealthy so I’m sure justice will escape her

Defamation requires a provably false statement of fact, that has been published, and caused damages, and that the speaker has some level of fault - for a public figure the level of fault is actual malice: knowledge that the statement is false or a reckless disregard for the truth of the statement.

The difficulty here will be proving damages.

Yep

Because of the FA, defamatory statements against public figures are not actionable in certain circumstances, so that means that such defamation is, indeed, protected by the FA

No. Defamation is not protected. There is a higher bar to prove the defamation, but if the defamation is proven, it becomes unprotected speech. If you cannot meet the higher bar then it is not, by definition, defamation.

But a statement can be “defamatory” even though there is no viable cause of action because of the higher threshold for a claim involving a public figure, because of the protection afforded by the FA

No. By definition a statement that does not meet the elements of defamation is not defamation.