We have the same thing as Juliet and it works great!
When someone in our house needs extra moisture, we use a vaporizer and add Grapefruit Seed Extract (GSE) to it. A few drops of it will kill about any bacteria/fungus. For a full vaporizor I would add around 10 drops, maybe 15. Usually we only use it for a couple of days but we clean & dry it each day.
Since your daughter is so young, you might try putting a couple drops of saline in her nose and using the nasal bulb. I used to do that for my daughter when she was just a few months old. Now she is 5 years old and does 8 ounces of saline once or twice a day!