Since you can’t make up your mind, let me try to help: It would be wise for you to listen to your psychiatrist and your mother. Your mother may be loving and supportive, but she doesn’t have the training and skills to help you deal with your feelings. Your psychiatrist is recommending that you see a therapist because it is just plain good practice. Symptoms like yours respond best to a combination of talk therapy and medication.
If you haven’t already, do make an appointment with your endocrinologist as well. Diabetes increases the risk for depression. In addition, high sugars and dehydration can cause what is called “fuzzy thinking” or “being in a fog”. That may be what you are describing as “slow.” Let’s make sure your lack of motivation isn’t a consequence of inadequate diabetes management.
You are an important member of your treatment team. If you don’t have the energy to step up and take charge for now, ask your mother to make those appointments (a therapist and endocrinologist) for you. You can feel better.
I wish you well.