Hi J.,
I'm a home child care provider and with one of my daycare girls she could tell us she had to go pee, should could go pee. she will tell you she pooped in her pull up bring you a new one and the wipes. All the classic signs of being ready to potty train, but and I mean BUT when it came to going poop in the potty it wasn't gonna happen. We tried for 2 weeks and she got really bad constipated. She would go pee in the potty but when it came time to going poop it wasn't going to happen.
In my opinion you are in the power struggle she has the last piece of her being a "baby" left. Shes trying to figure out the benefits to her pooping on the potty. And on the other hand you want her to go and she is the one who holds the power of whether she will go in the potty or in the toilet. I think no matter what age some kids are just ready when they are ready and some kids are not ready at the age they should be. In my opinion you should cut her a brake for a little bit. Let her know that you know she is a big girl and that she can poop on the potty but until she is reasy and so she doesn't ruin anymore panties it's back to the pull ups for a while. Give her the option to wear panties and let her know that if she wears panties she has to go poop and pee in the potty.
From the sounds of things she has had alot of change in her life in the last couple of months, with some kids things like this happen with their behavior, and things like this but hers is pooping in the potty. I would give her the oppurtunity to get used to her surroundings in "her time", it might take a while but it might be what she needs.