Our cockatiel just layed an egg. What do we do?
Single hens often lay eggs and it's usually more traumatic for the owner than the bird. When you first notice an egg has been laid, throw it away. If the egg laying continues, usually every other day, you might want to let her sit on them for two or three weeks to satisfy her maternal instincts.
A tiel that is laying eggs requires additional calcium and protein in their diet. As long as you provide those extra nutrients, she should be just fine but check her daily to insure there are no problems such as egg-binding. If you should suspect a problem, take her to an avian vet ASAP.