Silkie still broody

Well one of the silkie chickens is still broody and now she is broody with a vengeance. After asking for advice from a couple chicken groups I have decided to let her sit and see what happens. My concern in her young age, not quite 20 weeks old but if this is what she wants we'll give it a try. I removed the golf ball and plastic eggs which leaves her with 4 chicken eggs, not all of which are hers. Today, 9/15/16 counts as day 1 of 21.