Sensitive as in allergic. She sneezes and gets stuffy.

Just as another data point, senssuzy has multiple chemical sensitivity, which gives her the allergic reaction and (as a result) the super-acute olfactory sense. In that situation, candles are one of the first things to go. The only candles she can be around are pure beeswax candles. No scented anything. (No perfumes, no scented detergents or cleaners...)

So, I second canyonwren's comment: Ask around, see what everyone says they're OK with. An air filter sounds like a great idea.