Well, 160g for a 8 month old is a little small IMO so either she is a horrible eater to begin with or she was less since she was a "seller".

Switching over to F/T is something I have only done with 1-4 month old snakes... anything that has been fed over that seems impossible. I have a few snakes that will not take F/T not matter what I do. The best way to get a snake to take F/T is to just keep offering it. But at one point you have to draw the line and that choice is up to you. If feeding live is something that really bothers you, you may have to give up the female if she continues to refuse F/T.