I know this sounds awful, but pinworms are spread in the air and are found where children play. I am a pediatric advice nurse so the advice I am giving you is sound.
First off, don't make her feel bad or dirty...anyone can get it. It will require her to take a medication (ordered by her pediatrician) just once and repeat it in 2 weeks if she is itchy or you see pinworms. Only those who are symptomatic need to be treated.
When changing her bedding to not fan or shake into the air, any bedding as this can spread the pinworms and they can be swallowed. Vaccuum her room, or wash the flooring. Bag any stuffed animals or things that might have come into contact with her body. Put vasoline on her anus because she may have scratched herself sore. Clean under her fingernails well. That's pretty much it.
And, yes, inform her day care. A notice needs to be sent around.
Hope that was helpful.