I don't know what caused this, she's normal in every other way. I noticed when she lays down, she tucks her head into her wing though- that's different behavior. Any suggestions? Thank you!!
First I would look around her eye for a mark that could be a sting or peck. Then look for bubbles in her eye and any drainage from her nostrils or mucus from her beak. That could be from a respiratory infection/disease such as mycoplasma (MG.) Tylosin can be given in her water to treat that. Dosage is 1 tsp per gallon of water, and is available from jedds.com and here: https://thecanaryfinchstore.com/product/tylosin-powder-for-birds/