Poorly kitty

My cat has been acting really weirdly today, she's gone very quiet and withdrawn, moving very slowly and isn't opening her eyes fully. She's slept most of the day and I noticed this evening she has a runny nose ☹️ any ideas what this could be? I'm going to see how she is in the morning and take her to the vet if no improvement. She's only 11 months old

UPDATE: we went to the vets today and they think she may have cat flu and also an injury on her spine (maybe from fighting with her brother). Given her the anti-inflammatory drugs this evening and she already seems much better 😊