Have you tried with a live trap yet? It's possible kitty is coming out of hiding sometime in the middle of the night when no one is around and wanting in the house. If no one hears her she would go back into hiding. Try setting a trap up close to the door she left from and bait it with tuna. Hopefully you will get a good result from it and not trap some of the neighbours' kitties.
Have you asked your neighbours to check in their garden sheds, under their decks, anyplace a small kitty can hide in, under?