Is she a free-ranger who got into something the others did not have? Any reason to think she had something spoiled?
Separate her, she needs a shallow bath and drying, then time in a warm place. This will give you a chance to observe her. Pristine cage, fresh bedding and if possible a piece of 2x4 (wide side up) or 4x4 as a mini-roost. Use clean cloth as a cover to calm her so she can rest.
During the bath, gently examine her vent area, palpate softly and not anything out of the ordinary. Check her crop gently too.
Pay attention to possible prolapse of vent just in case. Prep H can help with this.
If you have it, place her on electrolytes with or without terramycin until you have a chance to see what is happening with her. If she will eat it, yogurt. Bonus if she will take chicken feed.
This will give you a sense of where her problem is going...so some of us can assist you. It buys you time to breathe and assess.