Jo,
I would offer it one prekilled large/jumbo rat. Since you don't know the temperment with this snake I would remove the snake from the enclosure first, place the rat in, then place the snake back in the cage (following proper husbandry rules of course: wash hand after handling rat and before handling snake ect.ect.ect.). Another way would be to use tongs to place the rat in the enclosure. That way the new owner can do it and not really have the risk of being bitten. Keep in mind the new owner should be the one doing all of this because it is her snake and she needs to get accustomed to these routine husbandry chores. Also it will help set up a routine the snake and her can be familiar with. I do agree someone needs to be with her to show her the ropes but I really can't stress enough that she needs to be the one doing it and not your husband. Good luck and I hope this helps.

Forrest