Howdy, my near-neighbor twenty-some miles to my West ... sorry your Covie's havin' such troubles.
Not sure how much help I'll be on this, but it sounds to me like you've been doin' the best you can by her ...
First thing is to keep her warm. Our weather's gone from moderately dry 'n warm to unseasonably damp 'n cold is such a short time that it's a bit uncomfortable, and she's surely in pretty rough shape already.
You'd asked about forcing food/water, and I've heard some say that's not a good idea ... but, if she's dehydrating, and her only hope? I'd consider it. If you do? Be certain the eyedropper reaches beyond the hole at the base of her tongue, so as to not push anything into her lungs.
That reminds me ... >
>peck here<< to see an interacting presentation of the anatomy of the chicken (move your mouse around each element for added information).
Although the comb turning purple can be the sysmptom of some diseases/infections, it's most probably a response to the stress her body is in.
At the bottom of my post, there's a link to help identify poultry diseases by the symptoms ... peck it, and begin runnin' down the list for anything that sounds familiar ... often, this helps folks spot symptoms they had previously not aware of, which helps to get to the cause, and any potential treatment.
Also, you need to keep a close eye on the rest. This could possibly be something that's gonna hit them as well. Try to always clean up and change shoes when you're headed towards your coop, so as to not potentially transfer what she may have.
I know I'm throwin' a lot at ya here, but it's sorta like how you felt ... when we don't know what's goin' on, we tend to do that.
One more thing you asked about .. here's
the best article I've ever seen on egg binding, just in case.
Hope she gets better. And, feel free to PM me if you need somebody to dig through the 'net for further informations ~'-)