Eliminate any sensory issues in the bathroom. Urinating is fast but the longer time spent pooping might be too overwhelming. Make sure the lighting is not harsh, and there are not sounds or smells which upset her. For my son, buying a padded toilet seat helped - the hard porcelain seat was painful for him. Good luck.

We also have a specific bathroom time (it's his after-dinner "business time"). It's a great routine, unless we're out somewhere and forget. Then it leads to an accident. When he first started potty-training, we sat him on the potty after dinner every night with a train book until he pooped.

When faced with the prospect of changing diapers when I had foot surgery, my husband poo-trained the little one on a schedule. After dinner/before bed, sat him on the toilet and told him to POO. When the kiddo pooed, he got to take a bath (that was a reward for him, but not all kids love water like that).