Hi, Annambrose, yes we're glad you've joined the forum as well, welcome.
Certainly sounds like sour crop, and if you have successfully drained it, you will have helped her. If it felt like a balloon full of water, and liquid came out, I would think that was her problem. An impacted crop would feel all hard and lumpy, and nothing would come out if you tried to drain it. If she were mine, I would take her to the vet ASAP, as she probably has some kind of gut infection, which might be cured by antibiotics, and the accumulation of fluid in her crop might be a symptom of this main cause. You might need several goes at drainage, when you see she is feeling worse again.