She shouldn't be able to hear him. The Doctor has disabled that implant time and time again, but it always seems to reactivate itself whenever there's another Borg presence, whether it be that of a few stray drones, One, or the Collective itself. Such seems to be true of Locutus' awakening, and it is imperative that the implant be returned to a state of dormancy as soon as possible, lest Locutus catch wind of what they're planning to do about him.
"I used to miss it," she admits, taking a seat to make accessing that implant easier for him. "The Collecitve, their voices. Now I find the sound of voices in my head that are not my own to be disturbing. Something that I once viewed as comforting is now cause for alarm."