Silence is still an answer! His lack of doing anything is an answer! In fact it is the loudest and most painful of them all because of this exact reason! With silence she has to guess and by guessing it leaves her open to misunderstand WHICH SHE DID. By not answering her, by remaining silent, he gave her his answer. It was up to her how to interpert it based off her experience with him. He failed his job as a husband when she ended up misunderstanding to the degree she did. He should never have stayed silent. While she has the chance to figure out the past and maybe even regain something later in the story this does not happen in real life. He would have regretted that for the rest of his life because he remained silent.