My sincerest condolences (yes, that is the correct word) to your daughter and I pray that she suffers no long-term harm. I empathize with what you have gone through and will go through. Although behavior and conversation may indicate that the past is forgotten, it never is, and never will be. I encourage you to actively seek out a professional counselor for your daughters.
Never feel you must justify you absence, life happens to us all and we all understand.
Your back and posting, that's the great part! May the rest of the year go better for you.