I am a big fan of homeopathic remedies, they do have worked for me and my kids in the past. You can find them at Wholefood Market.
This are three little things you can do:
Similasan Homeopathic nasal spary is safe for babies. (WFood market)
Baby Simply Saline (nasal mist) at Walgreens, Kroger or any store.
BABYRUB from Vicks... (please make sure is the one for babies) Rub it in her chest and back just before going to sleep.
And if possible put something, a pillow or anything UNDER the mattress in order to create a little inclination. Notice that when the baby sleeps in her chair or even a swing she breaths better because she is more upright.
Hope to have been of help, good luck!
PS... also maybe you could try the homeopathic teething tablets that are sold everywhere. I did not need them with my kids but I've heard they really work.