I struggle a little over the sentence in that passage you quoted "feelings make composure a disgrace, left her in no danger of incurring it. I think what it's saying is that she's worrying about making the appropriate(in her mind) show of sadness, but her actual sadness really did prevent her from sleeping, and she truly was that sad.

I see irony too in that sentence. Composure would be a disgrace, but isn't it more of a disgrace to give pain to your family by forbidding all attempts at consolation.

I can almost imagine her crying out all her true tears that first night, and then when her emotions start to settle down to say to herself, "Oh no, must remind myself how sad I am" and then re-create the sadness over again by playing those songs, etc.