Not knowing you or your mom or the exact circumstance , I have to wonder ,this from what you say is a kind of ongoing "quest" of your mother to have you evaluated ,is it possible there is something more troubling than covert narcissism going on ,say munchausen by proxy ? From what you describe that's my gut reaction ?
It is a form of abuse and possibly a devastating form of abuse because you as the victim of it could be diagnosed with something ? and marginalized for the rest of your life with an inappropriate "diagnosis" some tips

Until the age of majority you are under her thumb and she can have you evaluated till she is blue in the face,if nothing is there nothing will be found.
If you do not feel comfortable with the evaluator for any reason you can request someone else ? Easiest most proffesional way to express this is just by saying " i do not feel i can have a theraputic relationship with you and would like to terminate this session and resume with someone else " dont lie or be evasive,disrespectfull because those could be construed as something else.
Once you reach the age of majority you can refuse to participate , her only recourse would be to "throw you out" any parent that does that is not someone you want to be trusting of anyway .Psychologist are trained to "look and listen" and not be hasty , so participate, at worst they figure out something isn't right with mom and due to mandatory reporting will notify child protective and the police to investigate , then you are you are free to work on your anxiety with them ,at best they disregard your mother entirely and start working on what is troubling you .
They can help with anything you consider a problem ( something that Is holding you back from your full potential or happiness in life).
Try and remember that adopting a cat takes paperwork and proof you will be a good home, to be a parent takes much less (no paperwork or proof of a good home or stable life of any kind).

Be carefull stay safe !