it depends on what is the "Now Head of Department" going to do? Is he/she got promoted become yr boss or going to retire......If is first one....u can recommand her to be a head of some other dept which under u...if no 2...why should u bother to use her assistance....
Frankly speaking, I will not use the "old" assistance. First of all my assistance had follow me for 8 years, she "deserve" to be get promoted, if I can't reward her by doing this, I will not get credit from my staff cos they will think that I am useless and no point working hard for me. Secondly, since my assitance follow me for 8 yrs, she will know wat I want and I need not to train again.