It looks like a collapsed egg membrane from a shell-less egg. I would gently pull it out. Clean up her vent with a wet soapy cloth. Get some human calcium tablet with vitamin D or a tums, open her beak and give it to her into her beak to swallow. Repeat the calcium with vitamin D daily for a week. She may have a calcium deficiency, a reproductive problem such as salpingitis, or a shell gland problem. When they lay a shell less egg it can break inside, or there could just be parts of eggs passed. They may feel very weak when this is happening. Make sure to offer food and water when she feels week.