I believe very strongly that your wife has heard her bark. I heard our Jamaica bark from outside, the night she died. I knew her bark...and it was definitely her.
I've also had another show up in a photo, when she passed on....and I'm not even the one who noticed. A friend did. The photo was taken approximately a month after her death.
I believe that hey come back to let us know they're okay. Often, once we acknowledge that we've seen or heard them, they go on to wait for us at the bridge. But they're still watching over us, even tho we don't see (or hear) them again.
Many here have heard their dogs bark...or their footsteps...or the jingle of their tags...or a sigh...or even have felt them rub up against us.
Tell your wife that Catie wants her to know that she's okay...and will be waiting!