B.R.
It's probably something emotional that she's responding to since she didn't have problems before. Try this- tell her that, at least while you're at home, if she has to go poop or potty she has to pull down her pants and sit on the potty (make sure she has the tools to do this and can reach everything she needs to reach on her own). This will both empower her to take responsibility for herself and take some of the power struggle away from you. Then, if she has an accident, have her clean it up herself. I know moms have the hardest time with this because it can be messy, but it's important. Have her take off her panties herself, dump the poop in the toilet, put the panties and pants in the washer, and clean up any other involved messes (and wash her hands!). This should help her to take total control over the whole issue, which should cure it if it's a power struggle. Good luck!