... any input is more than welcomed and appreciated...
...how do I know when it is time for me to let her rest?...
One of, if not the most difficult question for all of us at one time or other.
Because you opened the door for input, I'll offer what I would do.
If one of mine were dealing with asthma, I would, first off, be part of a group of people dedicated to this one issue. There are two such groups that I know of: felineasthma : Feline Asthma & Respiratory Diseases
and Feline_Asthma_Bronchitis : Feline_Asthma_Bronchitis
During the past 14 years, more than four thousand people have participated there - that collective experience and knowledge cannot be surpassed.
Some years ago now (there are still days when that feels like yesterday, others when it feels like a lifetime ago) I lost a little one with FeLV - without advice, support, experience and in the hands of an incompetent Vet. Later, too late, I discovered the wealth of all those things that had been available in the specialized online FeLV groups - - if only I had known....
Today, were I in the same position, that's a question I would be putting to one of these groups for input. We all have our personal and situational limitations and out kitties are part of these, and any input must be weighed in consideration of them - BUT, at least I would have had and explored and considered that expert advice.
I'll be thinking of you both