Well, since the mystery train case, haibara death was faked by Conan, akai, and Kaito kid.
However, Vermouth is aware that Shiho did not die, since she saw Agasa holding her as they left, Conan was on the phone with Kaito kid.
Both Bourbon and Vermouth were around her and she didn't react once to any of them, in the episode " Jodie's Memories and the Cherry Blossom Viewing Trap "
Maybe she feels comfortable since she has her death faked to the Bo she doesn't feel anxious or they were too far form her for her to feel there presence around her.
If she no longer reacts, means that it could be vermouth, but I doubt it, I personally don't think its vermouth, so well see what Gosho has in store his time.