The most I might do is whisper in my GF's ear, "Sounds like your type of book." That would be 'sharing the intimacy of her confession' without putting her on the spot.
I do this regularly, pull my lover close in public and whisper in her ear that my thoughts are not on the lovely art deco table she points out, but on her naked body bending over the gleaming wooden tabletop while I take her hard from behind.
