Please stop being so hard on yourself. It sounds to me like you are grieving. You are still working through the anger and hurt and sadness of losing someone you loved and admired. It makes absolute sense to me that you feel like you’re in a fog. It’s normal and appropriate.
Meanwhile, the unconscious is a wonderful thing. You already had doubts about your choice of career. In a way, your grief let you do what you didn’t have the courage to do on your own. You gave yourself a way out by doing badly on the test. You and I both know that you can elect to take the test again. Many people are so nervous during their first try that they don’t do very well so they spend more time studying and take try again. You could too. But your mother’s reaction tells me that it’s been tough for you to simply have a rational discussion about a change of direction. You had to blow out to get out. Okay. So now you are free to think about law. Sounds fine to me.
Your mother is a pain for the same reason you’re in a fog. People grieve differently. Some people, like your mother, take it out on others. Some people, like you, take it out on themselves. Ideally, people love and support each other through it. Since it seems your mother can’t do that, I hope there are other people in the family who can. It’s important to remember, to tell stories, to share how much someone meant to you, and to mourn. If there is no one else who knew him that you can talk to, I hope you will consider looking for a grief support group. Many hospitals offer that service. You could start by asking your doctor for suggestions.
Please give yourself time. It often takes months and years to fully metabolize a sudden and senseless death. Right now you’re still in the acute stage. That will level off. But don’t be surprised if every now and then you feel overcome by sadness for a few minutes or hours. These “grief attacks” are often set off by a smell or sound or story that reminds us of the person we lost. They are expected and normal.
I hope you give yourself the summer to relax a little and to think through what you really in your heart of hearts want to do for a profession. You are clearly intelligent and disciplined. It looks to me like you can be successful at whatever you choose. You have reason to have faith in yourself.
I wish you well.