Sometimes we can see reactions when dogs inhale smoke, but asthma in dogs is not nearly as common as it is in cats. When they're having an allergic reaction to something, we tend to see facial swelling, possibly difficulties breathing.
Drooling tends to be associated more with GI upset and toxin ingestion. When they swallow something that upsets their stomach, for instance, drooling and foaming is often a sign of nausea. Some toxins will cause profuse drooling, and it is usually related to something that causes pretty severe signs (drooling, lethargy, vomiting, and an increase in mucous production. We call these SLUDDE signs, and almost always constitute an emergency.
Given that you're seeing two signs that are fairly significant when seen together (difficulty breathing, and salivation), I think it's best to pack her over to the emergency vet clinic. I know you say she's getting slightly better, but when it comes to difficulty breathing,if they take a sudden turn for the worst, you want to be at a clinic, when time is of the essence.
I really don't think this is related to the candle itself, but take it with you to the clinic just to be on the safe side. I would also make a mental list of things you have in your household to provide to the vet (indoor plants like sago palm trees, hops, pesticides, medications you take on a daily basis in case one got accidentally dropped). This can help your vet a lot when a situation turns dire, as they can use it to help treat her if she possibly could have ingested any of these.