I have a hen that has had this and both times once it got rock hard it required surgery.
For now I would forget about the bra as it sounds more like compacted crop.
Seperate her so she isn't adding to it with grass or longer to digest grains. You can try giving her something high in oil to get some lubrication going. I used her feed moistened with warm water with canola oil mixed in. Biggest problem is getting her to eat it as by then they pretty much stop eating but they will drink to try and move it. Keep whatever you give her to small amounts. 3-4 times a day try massaging the lump till it starts to soften. Will feel a bit like hard plasticine.
If after 2-3 days there is no improvement your only real option is going to be the vet and surgery. The crap came out of mine both times was never ever going anywhere without being removed by a vet. It was a huge amount of grass matter both times.
This is what they got out the second time, there was so much the nurse put her hand there to give a sense of scale.
(Sorry bout quality, was a photo of the photo on her phone). Had been over a week since she had eaten the grains in it.
After surgery no grains for weeks as they are harder to digest. Vet should give you antibiotics and a probiotic powder to add to her food to kick start the crop again. Keep her seperated and only feed her small meals of moistened feed for the first 2-3 days then slowly start adding small amounts of other soft foods till she is eating properly again.
The hard lump in her crop suddenly vanished two days ago but if I have a chicken in the future with an impacted crop I will remember this, Thanks!