my first thought was 'fish bone". I went home to get a carrier.
Brought her to the vet this morning and 4 fish bones were removed from her throat. How much pain she must have suffered... all because of such irresponsible lazy feeders who will throw fish with bones for the cats to eat. I have put up notices at the area.
I made a mistake by letting her out on the balcony as she is usually quite friendly. Luckily Mohan was in the area and could help me get her back into the carrier this morning.

Measured one of the bones...it was 2.5cm long.
I will probably release her back tomorrow, because she does not like to be confined. The vet gave long-lasting antibiotic injections.