We all make mistakes, yours was agreeing to go along with this. When people die others want to say goodbye and the only way they can do that is to attend the funeral.
Anyway, I am sorry that this caused you so much turmoil. You did the right thing in the end and thank goodness you have too. Things such as this can cause a family rift for years.
Probably your DM was feeling sad that those she wished not to be at the funeral did not visit your father when he was dying. She had a right to feel sad. Families should stick together and get over any imaginary slights.
Anyway all's well that ends well. You should not have been put in that position in the first place. We all show our grief in different ways, your DM seems as though her first reaction was anger, followed by regret, followed by a feeling that she did wrong asking you to keep the secret.
What a loving, caring person you are. The family feud will be over I expect now. All thanks to you.
Angela Rayner lashes out and calls Sunak “pint sized loser”.