well, please don't declaw it, most people don't know what that entails, it isn't simply "surgically" removing what we would think of as their fingernails. unless it's changed in the past few years it's basically guillotining off the end bone of their little fingers, NON-surgically (just a big clipper thing, usually). it's messy and typically mangles the tip of their finger, with either some of the bone left, or part of the next bone crushed, it's really sick and it can screw up their confidence, which can lead to more problems (read: peeing).
none of the shelters or breeders around here would ever give a cat to a person that planned on doing that.
i see that rhyno's beaten me to a couple of suggestions - i can think of four things: put a piece of cardboard (or whatever works) in front of the speaker covered in double-sided tape, no cat in their right mind (oxymoron?) would step on that. maybe you could get rid of it after they'd conditioned themselves not to get near the speaker, i dunno. (along the same line, if you could ever get something that played a loud noise whenever they stepped on it and put it in front of the speakers, you're done - that would solve it, but i can't think of what that might be.)
they do, as someone mentioned above, hate citrus smell, but i've never tried to deter a cat with it. you could try putting something of that sort near the speaker.
third, as i think someone mentioned above again, put some scratching posts near enough to the speaker that they see them, but not so near that they make associations.
or, lastly, you could just block them physically - i have some gallo micro speaker stands, for example, that are just thin poles on a weighted base, and if i put them in front of a pair of box speakers without the gallos on them, they would sort of block the grills without doing anything noticeable to the sound. seems like any pole would work.
ironically, the easiest thing would probably be to just keep screaming at her until she gives up doing it and have a second set of grill covers handy for when people come over...
good luck, that is annoying, but cats is cats.
