I need help with bereavement benefit claim

My mother died on the 15/01/2019 the funeral cost £4,100. I lived alone with my mother and am on Universal Credit, so there is no money to pay for her funeral bill.
I spoke to some one at the government bereavement phone line and the day I called I was very upset about my mother and had taken anti depressants and pain killers. So I don't remember much about the phone call. the bereavement officer bombarded me with questions and coerced me into saying things which where not correct. He asked if my brother and sisters where working and therefore liable to pay the funeral bill. My brother and sisters had nothing to do with my mother for years because of her alcoholism. I sent in the form for the bereavement expenses and it was rejected on the basis that my siblings could pay the bill. I am going to appeal and this has to be sent no later than the 21st of March 2019 if I date it as such.Can I win an appeal and what do I put on the appeal letter to win.

Any help would be great baring in mind I have to send it on the 21st of March 2019 at the latest with that date on the letter to be in the 4 week appeal time.

Niks, I am sorry to hear you are having such a sad time and send you my best wishes.