If you are monitoring her weight that is good. If it was my snake I would keep trying until a few more grams were shed. But also wouldn't go on too long because of the age. There is no exact answer you just gotta try to balance it in your own way. If you feel she will be ok going longer go ahead. If you feel it is too much of a risk to wait it out then don't. It kinda depends on the health of the snake.
Personally I think most people give up too soon with reptiles when it comes to changing eating habits but it's still their choice.