And yet she's shown a solid history of the advice's complete ineffectiveness (or her belief in its ineffectiveness) when a frequent commenter on her favorite message board is causing her "undesirable peripheral psychological" harm by virtue of her extreme dislike!

Of course her advice is ineffective if one has decided to dislike someone. But this is no mark against her, because her advice is entirely about what to do after one decides not to dislike someone.

If that's not relevant to showing her advice to be phony, what would be?

What would be relevant would be a case where she had decided to like someone, applied the advice in the OP, and yet failed to like the other person. Also relevant would be a general theoretical argument that the techniques in the OP wouldn't get you (the general you) to like someone even after you had decided that you ought to.

And why should I have stayed silent on the existence of these two Alicorns?

Because your criticisms do not address the OP.