All he/she needs to know in the email is that you're seeking a therapy which is within her scope of practice, and what sort of day or time is suitable for setting up an introductory interview.
So something like
Hello Mr Therapist,
I was recommended to you by <whomever>, and hoped to set up an introductory interview to discuss the possibility of therapy.
(optional sentence here about what you want therapy with - this can wait until the interview if you want more privacy than email offers)
I am available (mornings, evenings, nights, outside normal working hours, with a week's notice - whatever applies), and look forward to hearing from you.
Seshat's self-help guide:
1. Would you rather be right, or get the result you want?
2. If you're consistently getting results you don't want, change what you do.
3. Deal with the situation you have now, however it occurred.
4. Accept the consequences of your decisions.
My professional areas of expertise are computing and writing: I am not a doctor or a lawyer.
When your health, freedom, etc are at risk, always see a professional.