Hmm... that's tough. Maybe you can think of a different way to ask her to repeat herself. You could say that you are really sorry, but you feel like you are losing your hearing. Blame it on yourself... let her know that you think you are going to get your ears checked. I know it sounds sort of silly, but it's better than her getting angry and getting down on herself, feeling like she is old and not able to communicate well anymore. Also, try to sit close to her and really pay attention when she talks. Try changing your attitude and being super-nice.... this will make it difficult for her to be mean to you.