Okay, Harry had Lasciel's shadow in his head for years. Further there was a connection, though blocked, from Lash to Lasciel.
Here's my theory...
When Lash sacrificed herself, she and Harry created Bonnie. And we know that Lash wasn't 100% gone, because she was still able to help Harry with his Guitar Composition.
This suggests that the link between Harry/Bonnie and Lasciel may have still had some life. So, when Harry busted the coin out of his vault, and gave it to Fr. Forthill, Lasiel was able to take a "reading" from Harry. While she could no longer exert any influence, I think the link hadn't completely been destroyed. I think that since then, Harry's healing has closed those holes in his brain, completely cutting him off from Lasciel, but she still had "Read access" to his mind for awhile.
I do not believe she has any access to Bonnie. But who knows?