I think the best thing to do is what I tell people when they call.... if you can get close enough put a paper collar on her to double check she's stray saying something like; 'this cat appears to be a stray, if she is your cat then please call xxxxxxxxxxx' if you haven't heard in a week then call CP or other rescue who should get her on their waiting list. My branch would consider a stray a very high priority as there's the risk of being unneutered, she will then hopefully get a nice rescue place soon and although kittens are desirable by lots of people, there are lots of homes that are happy to take on an older cat, especially those in slightly busier areas where they wouldn't be given a kitten or young cat by a rescue. She will find a lovely home, even if it does take a little bit of time in care.
Keep feeding her until she can be taken in but if she doesn't want to come in, I wouldn't push it as it may stress her and also your other cats. I'm sure she has found a shelter, cats are very resilient and there is always the chance that she does have a home- she just appears to not. Therefore, the collar is always a good idea cause I know how I'd feel if my cat suddenly disappeared!
