Hi there -
Went through this recently with my old lab cross, bless her soul. Buy yourself a big box of medical gloves, non latex if you can, and, not a pretty thing to discuss, insert your finger into her bum. Should stimulate a BM right away. Not a nice thing to have to do, but the options are limited. Good luck! I think if she still enjoys most of her life, she's not ready, dignity notwithstanding. However, everyone has their own limits, you gotta do what is good for you too. My thoughts are with you.