I would email the area manager and cc your bos
Something along the lines of:
Further to my complaint to my manager (insert name) on (insert date) regarding an issue I am experiencing with a colleague, (insert bully's name) who is continually bullying and intimidating me, I am disappointed that I have received no further communication regarding the issue.
As you are aware, I have had a long standing, serious issue regarding bullying and general intimidation by .....
This has been ongoing for several years, despite repeated attempts by me and my manager (who is copied into this email) to resolve the problem amicably. I have made complaints on many occasions and whilst the matter improved initially, after a very short period of time, her behaviour towards me has once again deteriorated.
In summary, whilst not exhaustive, the following will give you an indication of what I have been subjected to over x number of years
(Insert bullet points of the most distressing issues. Do not be over emotional, or try to list every single action, as this may detract from the most serious issues)
As I am sure you can appreciate, this has become incredibly stressful and is having a negative impact upon my work and private life.
In view of the above, I would therefore like to escalate the issue and make a formal complaint regarding (insert bully's name) and her appalling behaviour towards me,
Could you kindly let me know the relevant process?
I look forward to hearing back from you shortly.
Kind regards