While asthma would be helped by albuterol if this were related to heart disease then albuterol can be contraindicated, as it may raise an already fast heart rate making her heart function even more inefficient. I understand that you were trying to do anything to help but I don't recommend starting therapy without a better idea of what her primary problem is.
Thank you for your email. I do think that there might be more going on than stress, and kittens are prone to infectious diseases. If you don't trust that veterinarian that you saw, it would be a good idea to find a second opinion, even if you have to travel a bit to do so, as he could have a problem that needs to be treated. You can also call your veterinarian, let them know that he isn't getting better, and see if they have any other recommendations for him.
Last, but maybe most important is, if you can pay to see wild cats on your terms (ie: cheaply, in a cage, or being forced to let you touch them and have your photo with them or their young) then you aren’t learning anything about who these animals really are. You aren’t learning about how they fit into a complex environment when they are housed in a situation that does not duplicate all of the web of life that they are a part of in the wild. All wild cats roam territories that are calculated in miles, not square feet. To know anything about them, you have to see who they are in their real environment.
There are various different causes for rapid breathing which may include infections, pain, heart disorders, dehydration among other causes; a cat’s respiration should be below 30 breaths per minute when at rest but if it is significantly above this rate at rest I would suggest visiting your Veterinarian for an examination to determine a cause. Regards Dr Callum Turner DVM