You can put a humidifier in her room, cool mist is the best. Also using a nasal syringe a few times a day (before naps and bedtime) will help clear things up. You can elevate her head on a pillow while she sleeps with supervision, or have her sleep in a carrier or swing.
Don't worry about pushing solids if she doesn't want them.
Since she is stopping breathing, I highly suggest you take her into the doctor right away. That's a more serious effect of the flu, and should be handled professionally, especially in one so young.