Impacted crop or something else?

Two days ago I noticed one of the girls acting oddly....in hindsight she was off the day before as well. When I picked her up I was shocked at how large her crop was - seriously, it was gigantic, very soft and squishy. Her beak smelled horrible and she very obviously had some sour crop going on. I locked her up in the 'henitentiary' and did some research, and when I picked her up an hour later just the action of lifting her caused her to vomit. Because of that, I decided that vomiting her was going to be my best option. It took MANY times of upside down and breathing breaks, and the amount of fluid that came out was crazy, but she immediately perked up and had this look of relief on her face (if a chicken can show relief). I let her rest, then gave her a bit of scrambled egg with probiotics and electrolyte water, then left her for the night. Yesterday morning her crop was still large, but hard this time, and I could feel what I think was the corn she'd pecked up the day before - obviously her crop wasn't emptying. Several times yesterday I syringed oil and massaged her crop, trying to move the blockage. This morning it's much better, but her crop is still the size of a golf ball. Her demeanor has improved 100%, she's chomping at the bit to get out in the yard.

She's fed layer crumbles and I treat them with cracked corn daily. They free range on an acre all day, every day (including bare ground in the garden) so I think she's getting plenty of grit. What I *think* may have happened....our lawn got a little out of control down in the back, and when I mowed the chickens had a ball. I'm guessing she gulped down a bunch of too-long grass, and it's wadded up in there?

So what do I do? Keep on with the oil and massage until it dislodges and moves through? I helped a lot yesterday, this morning the crop is about 1/4 of the size that it was yesterday evening. Any tips or advice? Thanks!