I am sorry to hear about this concern for Cocoa.
Well, at 8 years of age, some basic testing should have been suggested for overall wellness evaluation unless a blood profile and urine test was done in the past year. Unfortunately, the vet can't really vouch for overall health without those internal tests. It would be no different than you and I going for a check up. The doctor might listen to our lungs/heart, look in our ears, check lymph nodes. But, does that really tell us anything about our internal functions, liver/kidneys, etc..?
So, with her change in breathing, that warrants a more immediate vet visit today for a recheck evaluation. We don't know if this is due to pain, nausea, or a primary lung issue. Not sure about the lip change, although there are neurologic conditions that can cause a acute change to the lip position.
Very sorry that Cocoa doesn't feel well. Even something like a urinary tract infection could cause some of these symptoms.
Wish I could do more, but convinced this is worth a visit today, and at least a basic blood and urine test.
Hope that information helps