If you can't remove the nest, or they put it right back, maybe you could sprinkle some poultry dust in their nest?? I don't think it would hurt them, if you use the .25% permethrin, like Hi Yield Pet/Livestock dust. They may not appreciate being treated for mites, and may decide to find a better place to nest! Just an idea...
....or she might appreciate having a parasite-free nest and raise more babies as a result.