The poor thing has gone from home to home to home. Wasn't always fed regularly. Lived in a dirty conditions. Dirty litter box. Sometimes no litter.
I don't know her temperament but I'm of the opinion that cats who feel safe and loved are generally fine and will be or become more social.
I'd bring her to the vet before letting her meet Alice and Francie. They are the main reason I'd hesitate as Alice has taken a year and a half to get to like Francie and they are still not exactly close.
I wanted to get another, younger cat for Francie to play with.
What do you think? Should I give poor Coco a chance at a safe, good life? Sara said ti would be a few weeks of fostering which I think is BS. No one is going to adopt a middle-aged black cat in a shelter. And I wouldn't put it beyond Sara to just turn Coco out.