I have a roommate problem....?

One of my roomies (Sammy) is a little OCD and I can deal with that. The other one (Polly) is the exact opposite of OCD and I can deal with that too. But Polly never does her dishes and that really bothers Sammy. How do I make Polly do her dishes without having to confront her? I want to avoid all awkwardness. And Sammy is too shy to talk to her or do anything.