Hello, I'm Dr. Deb.
I recently came online and see that your question about Bella hasn't been answered. I'm so sorry that you've had to wait for a response, but if you still need assistance, I'd like to help if I can.
If Bella is in severe respiratory distress, then I hope that you've taken her to an ER vet by now. However, if her breathing isn't that extreme, then she may be suffering from Feline Asthma. This condition is similar to asthma in a human in that there is inflammation in the lungs which is triggered by something in the environment such as pollen, smoke, aerosol sprays, etc.
Feline Asthma is often is a difficult diagnosis to make with certainty. Chest x-rays might be suggestive as would bloodwork (eosinophils might be elevated but they aren't in every case). I often diagnose this condition based on a cat's response to steroids. If they are 100% better, then this is the diagnosis in my opinion until proven otherwise. It may seem like a crude way to diagnose this condition, but cats tend to tolerate steroids better than any species I know.
Unfortunately, there's not much that you'll be able to do for her at home although I wish that weren't the case. If she continues to behave this way, then a vet visit tomorrow would be wise.
I hope this helps although, again, my profuse apologies for the delayed reply. Deb