Em-dashes in Speech Tag in Elmore Leonard

I thought some of you might be interested seeing this speech tag implemented with two em-dashes and a non-finite verb (the ing-form "raising"). 

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[Dawn gives Joyce a "reading"]

Dawn said, “Let’s see,” and turned over three more cards. “The Knight of Pentacles, the Seven of Pentacles, and”—raising her eyebrows—“the Knight of Swords. Okay, you have to understand I’m reading from vibrations, too. When I access your higher self I’m no longer reading the cards. If you want me to simplify this, not tell you what the cards mean… It looks like you have a choice to make, the Knight of Pentacles or the Knight of Swords. Do you know what I’m talking about?”

“Go on,” Joyce said.

Elmore Leonard,  Riding the Rap

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Now, one could see it either as an elision from '—[she said], raising her eyebrows—', thus as a speech tag proper, or just as an adverbial phrase introduced by the narrator,  conditioning the speech, when the speech/dialogue verb 'said' isn't considered to be there.