She left her child in her crib without tying her wrapper; what should she do?
Question

                I had a little girl and she died at the age of seven months. 

The cause of her death was that she was sleeping on the bed and I had wrapped her with the cloth only, without tying it, then she rolled over onto her face and I was not with her, and she suffocated. She was my first child but this was not the first time that I wrapped her loosely when she was sleeping. I had gotten used to putting her like that most of the time, and usually she undid the wrapper herself. 
That is why I did not expect what happened. 

Do I have to offer any expiation?.
Praise be to Allah.
      Firstly: 

    The expiation for killing and the diyah is only required from 
    someone who kills another person by mistake either directly or indirectly, 
    as al-Hajaawi said in Zaad al-Mustaqni‘ (p. 222): Everyone who kills 
    a person directly or indirectly must pay his diyah. End quote. 

    Killing directly means, for example, shooting at an animal 
    (when hunting) and hitting a person instead, or rolling over another person 
    in one’s sleep and killing him. Killing indirectly means, for example, 
    digging a hole in the path used by people into which a person falls and 
    dies. 

    With regard to killing directly, there is liability in all 
    cases. With regard to killing indirectly, there is no liability or expiation 
    required unless the one who did that overstepped the mark or was negligent. 

    It says in al-Mawsoo‘ah al-Fiqhiyyah (28/280): The 
    general principle is that if the killing was done directly, there is 
    liability even if it did not overstep the mark; if it was done indirectly, 
    there is no liability unless he overstepped the mark. 

    In Qaraaraat Majma‘ al-Fiqh al-Islami (p. 81) it says: 
    The one who does it directly is liable even if he did not over step the 
    mark, and the one who did it indirectly is not liable, unless he overstepped 
    the mark or was negligent. 

    The difference between overstepping the mark and negligence 
    is that negligence means failing to do what is required of taking 
    precautions, whereas overstepping the mark means doing actions or using 
    things in a way that is not permissible. 

    End quote from al-Qawaa‘id wa’l-Usool al-Jaami‘ah, by 
    Shaykh ‘Abd al-Rahmaan al-Sa‘di, p. 62 

    Secondly: 

    From what you said it does not seem that it was the result of 
    any overstepping the mark or negligence on the part of the mother, because 
    it is customary to leave children of that age without tying their wrappers. 

    Therefore the mother does not have to offer any expiation, 
    because what happened was the will and decree of Allah and she had no hand 
    in it.  
We ask Allah to 
    make this child a cause of her parents entering Paradise. 
And Allah knows 
    best.