I find it sad when people blame an animal behavior problems not on them selves when 99% are the fault of owners not understand the needs of the animals. Every single pet Ive placed has been great. Ive literally only had one issue after 8 years a lady moved, husband died and the was scared of her new home. That not because they cats a hybrid! Any cat would act unsure in a new home.
I cannot think of a connection between the running after another cat and the symptoms that she is presenting with except possibly hypoglycemia (normally causes an increase in appetite) due to the blood glucose level being too low. I would suggest to rub a little corn syrup or honey on the gums to see if there is any improvement in Cupcake’s symptoms; ensure you keep Cupcake hydrated and visit your Veterinarian on Monday morning, if the symptoms increase in severity visit an Emergency Veterinarian. Regards Dr Callum Turner DVM
Rapid breathing (tachypnea) is a respiratory disorder characterised by abnormal breathing that is rapid and shallow. It is caused by a reduced level of oxygen, mechanical disorders (where the lungs aren’t able to expand as they should, usually due to a build-up of fluid in or around the lungs), and physiological disorders in which the cat’s respiratory centre in the brain is over stimulated.