Thanks for your reply. Thankfully I think the situation is resolved now. Jakob settled last night and I went to work this morning. I let her out when I got home. She wouldn't fly so I carried her to her play area. She was still struggling with balance, but I could see the feather I suspected was causing the issue was still hanging out.
She'd pretty much not eaten all day so I placed her right beside her millet and she started to eat and eat and eat. She eventually wanted to move to a different branch and looked at it many times before she jumped.
She started preening again, and the minute the feather fell out she chirped. I picked her up and she flew back. We tried a few times and she's fine flying again.
She flew to her cage early and went up on her swing. She not asleep but completely calm now. It's early still but I've covered her cage as I think she's tired after this ordeal ?