I think he was wondering why he didn't think of texting Miriam and saying he was coming over. I think the last three panels are meant to be read as Adrian Texts Miriam about coming over -> Miriam gives creepy reply -> Raven & Adrian react.
I think you're right about the last three panels, although it would have been clearer if we'd seen the message he was sending. And it still doesn't really make sense. He took Raven's phone off her when she was (I assume) leaving a voicemail for Miriam, and he told her then that
he'd tell Miriam what was going on. I'm assuming Raven was using her own phone, although I don't know why she would have Miriam's number, and Miriam didn't recognize the caller. But we know that Miriam and Adrian communicate via phone. Did he actually try calling Miriam? She's supposed to be his slave, so he ought to have expected her to respond. And if he did try and fail, did it
really only just occur to him to try texting her instead?
Heaven forbid that I should ever overthink these things, but it would also have been useful to see whether his message mentioned Jacqui's place. Because the wording of her answer implies that she knows that he knows where she is, but it isn't worded as an answer to the question, "Are you at Jacqui's?" or anything like that. So maybe it's Miriam's display of this knowledge that Raven finds creepy (although fortunately Raven likes creepy things). It perhaps implies that Aiken and Amaltheia arrived and weren't successful.
Theoretically, if the soul-altering is able to bend people to her wil, she now not only has Erin but also Aiken, two very powerful sorcerer/witch/magic wielders on her side, and as Aiken demonstrates, she’s fully able to use that soul-suck on men.
As I've said before, I think the all-new Erin won't believe she was ever a powerful witch. That was just a delusion. I'm not sure if Aiken has powers.
However, I suspect Adrian knows about the magic touch, and maybe other stuff about Miriam. Although, you know, the texting thing suggests knowing about things isn't the problem with Adrian.