I second Yosemite. A sneze here and there...no worries. But if she slows or stops eating, starts having nose/eye discharge that isn't clear, etc....take her to the vet. More than likely they will just give you a basic antibiotic to give her for a week or so and then she should be good as new.
If her head gets stuffy/congested:
- Wipe her eyes and nose with a warm wet washcloth. Kitties can't blow their noses or wipe their eyes well when they feel bad.
- Try steaming up the bathroom or putting her in a room with a humidifier. When Anya was sick with a URI when we got her she slept in our room with us with a humidifier on full blast and aimed at the bed. Worked wonders.
- Feed her smelly wet food or tuna. If a cat can't smell their food they aren't usually interested. Often why kittens who are really sick don't want to eat. Plus this gets more moisture in her diet.
Good luck and I hope your kitty feels better soon!