Hi phil hope you feeling a bit better...
once her time is up I would send her this letter...
customers name and address
RE: NOTICE OF INTENDED COURT PROCEEDINGS
Despite several reminders to pay my outstanding invoice, no payment has been received for works carried out at.......(her address here)
This is to notify you that if no payment is made within seven days from the date of this letter, we will be proceeding with legal action to recover the debt without further notice.
I enclose a copy of the outstanding invoice.
Yours sincerely....
send this recorded delivery, cost about £1.50 from the post office.
I used this on a couple of plumbers that owed me over a grand and 2 days after reading this letter paid in full...Good luck mate, hopes it works out for you..