I haven't tried on carpenter ants, but I have always solved ant problems with a borax/sugar/water mixture (like so: http://www.mashupmom.com/yes-borax-got-rid-of-the-ants/). You wouldn't want your cat to eat it, but you ought to be able to set it up in a cardboard box with a small hole cut in the bottom edge, or something like that that she couldn't get into.