If she has a crop issue, I would get some unmedicated chick crumb and soak it in water to make a very sloppy mush and remove access to that feed. The aggregate nature of the feed will just add to the blockage. You want something that has no lumps in it and will just filter through the blockage with the water and massage. Chick crumb is also usually higher in protein which she will need to build her back up. Adding a little scrambled egg to the chick crumb slurry and some oil may also help. Has she lost weight/body condition? To assess this, feel her breast bone. Bearing in mind it is still winter and very little food is going through her system, a heat source will benefit her as she is not ingesting enough calories to keep her body temperature stable.
What sometimes happens is that they peck at long grass or hay and it gets ravelled up into a soggy knot in their crop and acts like a strain for food going through their system, filtering out the larger particles and only allowing fluids to seep through slowly. Poops become small and mostly liquid because that is all that is going through their system. Unfortunately the feed you are using does not help this because it cannot be broken down in the crop, so that creates a further filtration bed in the crop. I am one of those people who has concerns about this type of feed and
I would urge you to consider a pelleted feed for all your flock when this episode is (hopefully) resolved. I have outlined my concerns and the reasoning behind them on a number of posts recently where people were having serious health issues and even deaths whilst using feeds like these grain mixes and I will cut and paste them for you if you are interested, but getting her well is the priority.
It may of course be that there is a blockage lower down her digestive tract perhaps caused by her reproductive system, that is causing the food to be stopped back to the crop, but a crop impaction is probably the only part you can treat, aside from lubricating and massaging the vent, but it is probably too long since she laid her last egg for it to be egg binding and her still be alive and she is not obviously pulsing at the vent, which you would expect to see if that was the case.