She is sat on my lap now and seems fine and settled apart from a very swishy tail. Her eyes are normal. She's not distressed. So it's not an emergency or immediate vet visit based on that.
However, about half an hour ago she was laid happily on my lap and suddenly stood up, swayed about so I had to catch her, dropped her head and started hitting it with her front paws. Then she fell on her side and lifted her back legs up like a rabbit and pushed her front paws through them all while keeping her head down and flexing her paws open and closed. She was tense.
I don't know if her eyes were open as I didn't want to start messing about moving her.
This all took a few minutes (enough for me to realise she wasn't just being daft, call my husband over and him to actually come over).
Then she relaxed, seemed a little disoriented for a moment and that was that. She sat up, looked about and laid back down on my lap like normal.
Edited - Husband has just put food down, she was a little slow going to it but jumped down and walked over normally.