If she's sick then she's likely a threat. It depends on what's wrong with her. The last bird I had like that actually had cancer. By the time they don't want to move, they're very sick. If she's been sick a while, then they've already been exposed.
Nothing will treat worms AND bacteria. It could also be a viral infection. I just said clostridia because that's what mine had. It could be dozens of things.
If one bird in a flock has worms, they all probably have some. That said, a healthy chicken can handle a light load of parasites with no problem.
How old are all the birds?
Many of the things that can afflict chickens have no effective treatment.
Go on google, enter your zip code, click on the map on the right, hit 'search nearby' and type veterinarian. Start calling every one starting with the closest till you find one that will do a fecal sample.