If persusis isn't controlled by the "herd" vaccination process, and those without vaccination are at an increased risk of contracting it even in a fully vaccinated environment, then I'm not sure how its all that relevant that another child in the day care doesn't have vaccinations.
I think not getting your child vaccinated is about as dumb a thing as you can do, and I think there is 0 science behind it, but I'm certainly not going to tell/force people to do it. Yes, it sucks for this woman's child, and I feel for her and her child. But the reason we have freedom is so that you aren't forced to do something that could be against your interests.
Its possible, highly unlikely, but possible, that the nonvaccinators are correct. Do you really want to take the chance to harm or kill even say 100 children so that your one child can have that "magical experience." Of course you do. Should that mean that everyone has to do what you want them too so that your child can have that experience? No.
It sucks, but the world and the people on it aren't here to give your child a magical experience. Plus, there are 100s of other magical experiences for this child. Nearly everything is a magical experience for a child in one way or another. We as adults and parents sometimes allow our experience with the world to shade and cloud a simple fact... that we've experienced it and are bored with it doesn't mean that a child encountering it for the first time will be.
Celebrate that whatever experience your child ends up with will probably be a magical one for the child that he/she will remember and best of luck fighting the disease!