How does Blanche respond to the doctor and matron’s arrival Scene 11?

When the doctor and a matron appear, dressed in institutional garb, Blanche goes to the door, expecting Shep Huntleigh. She becomes afraid when it isn't him, and she backs into the apartment. The matron follows her in, and approaches her sinisterly. Blanche tries to run away, but the matron catches her. Stella tries to stop them but Eunice holds her back.