Forgiveness is a very necessary but difficult thing to do.

I am responding to someone who has difficulties with the memory of her mother.

I am very sorry that you may not have had the loving, caring, and embracing mother that you should have had. Going to the funeral or not is not necessarily important.  What is most important is for you to get rid of the feeling inside your heart about your mother.  Not because it is important for your mother, but it is important for you.  A lot of people hurt others, voluntarily or involuntarily, and it is very hard for the person on the receiving end to go beyond that hurt but it is necessary for the well-being (physical and spiritual) of that individual and the well-being of everyone around as well and the children if you have any.

A person that my late husband had great regard for was Viktor Frankl.  He was an Austrian neurologist and psychiatrist as well as a Holocaust survivor.  Please research this individual and read his book.  You may also watch this short TED talk, the English is not really good but good enough to understand what he has to say.
https://www.ted.com/talks/viktor_frankl_youth_in_search_of_meaning

If you cannot go to your mother’s funeral because it will hurt you in a way that will endanger your stable self then don’t go, what is important is your own mental and emotional stability because if you are not stable then others will suffer too.  It is not selfish to take care of oneself, it is necessary for the sake of others.

Mother Theresa said to her sisters that they had to take care of themselves if they wanted to take care of others (they had to sleep and they had to eat).

I hope that what I am telling you will help.  Be the best that you can be regardless of the shortcoming of your mother and others.
Sincerely,
Anne-Marie