Yes, Ammonia will kill mildew on blinds or curtains , BUT, Ammonia is very toxic, volatile, very damaging to your eyes, respiratory tract and skin. Ammonia can cause burns or rashes on skin. If ammonia is mixed with chlorine/bleach containing products it can produce deadly chloramine gas. So, it would be wiser not to use Ammonia!! Many household cleaners contain ammonia. To clean curtains/blinds, one can brush the mildew spores off with a hard brush, then rub with bicarbonate soda OR vinegar OR hot water OR with a cut lemon dipped in salt before washing with SOAP.

Hope that helps you. The best way is not to get mildew at all. Good air circulation and keeping the humidity low is a good way to prevent it.