The voluntary contributions would not be counted for the year of her 66th birthday.
They only count contributions for the averaging method for the last complete tax year before the pension is started.
If she was short reaching average 19.5 at age 66, she would have to wait until 1st January of the next year to start her pension with the extra voluntary contributions included.
If this turns out to be the case remember that 1 extra year will be added to her averaging divisor.
Hopefully she makes 19.5 at 66.