L.,
I know how helpless you can feel when your little one isn't feeling well. Several suggestions here have been great ones. The car seat option always worked for us when we needed it.
I would opt for a warm mist instead of a cool one, as the cool mist tends to cool down the temp in the room as well. You can always just use a small potpourri simmer pot with plain water. That works great to moisten the air gently.
Saline to flush out the sinus is a wonderful idea as well. But since she's not running a fever of any kind, and the use of any analgesics in infants (Tylenol and Motrin) is ineffective as is the use of OTC cold remedies, I would opt for something a bit more natural like Cold+C from Hylands. Lots of drug stores carry this now. I know Rite Aid typically has it. You can call around.
If you happen to be nursing, milk dropped in both the eyes and in the nose will help to keep the sinus clear of any infection. I usually express into a shot glass and have a glass dropper I sterilize before hand and use to apply the milk.
Wishing you and your little Ashlyn the best.
Blessings,
Rolinda
Wife, Mother, Friend