Examine why Melinda's mind is locked.
I edited the original question because it was far too vague, so I interpreted it in a broader sense that might get to its heart. The idea of Melinda's mind being locked is initially caused by the trauma of being raped. In a sense, Anderson constructs rape as a condition where the victim is locked in a perpetual closet of time where they are only able to interact with the horrific memories of the moment. Melinda is locked into this condition after being raped by "IT" and the social ostracism that follows. For Melinda, she is locked in her own memories of the moment. Yet, she is also locked into a condition whereby society does not really want to validate her voice. It is for this reason that Melinda is socially locked. The metaphor of the closet is important here. Melinda finds that she has to take refuge into a closet to "lock away" her own pain and suffering that is being endured on both internal and external levels. Where Melinda advances is that she comes to realize that if she does not pry open the lock of her own past, she will eventually become trapped by it. Through this, she "speaks." The element of learning how to "speak" is where Melinda is able to unlock herself and her own condition. It makes sense that "IT" confronts her in the closet, and it is here where Melinda breaks open that internal and external lock that is preventing her from finding happiness and some level of validation.