I find that letters from the clinic can take over three months to reach my GP - and only if I chase.
Would be interesting to know where your consultant is based, but I also find that the letter is an incorrect interpretation of the appointment.
Dont put up with it - tell them you are not happy and make sure the review is correct - it is important to get the correct treatment for your Mum. I have been battling for the past 10 years to get the level of treatment I feel I am owed,but it is constant.
Considering that stress is the last thing PD sufferers need, your Mum is lucky to have you looking afteer her.
Best of luck with sorting this out