What is the likelihood that my cat will return home?

If she has a chip id i would contact the carrier..also call all the shelters around your area including any dog pounds..she might just be hiding some where. Sounds to me that you are doing all you can...just keep doing what your doing walk the neighborhood with her favorite food and shake the bag. My one cat got out one night I walked the hole place couldnt fine him but the next morning he was sitting on the porch mewing that he wanted in. Plz keep in touch I hope you fine her soon. Good luck