Hi! I'm sorry your child isn't feeling well. There's not much that is recommended for a child of this age. The vaporizer is a good idea. You could give Benadryl (diphenhydramine) which would help with the sneezing and runny nose and is also pretty good at helping nausea. If you'd like to reply with her approximate weight I can help you with dosing. If she has these symptoms for more than 10 days without improvement or if she develops fever over 101 for 72 hours or more you should have her evaluated. Usually day 5 is the worst day of the cold and then things get gradually better after that.
Feel free to reply with questions/clarifications as needed.
It doesn't sound like the Hayland's has helped much so far. If she's average size for her age she can have about 1 1/2 teaspoons of benadryl (it should be 12.5mg/teaspoon but check the bottle to be sure). The saline spray is fine to help clear her nose a bit but won't help the symptoms go away any faster.
It's not uncommon to average a cold every month when a child first starts daycare. So long as she has the cold symptoms for 10-14 days, followed by period of wellness for a week or two before starting the next cold, that sounds normal.