I did the same with my boy once. We have a Mickey Mouse phone with a demo button and it starts moving and making sounds. I was holding my boy and made a jerking movement, to surprise him or so with a mind set of "oh geez, what is this all the sudden"...
What was I thinking, so stupid... I instantly made him afraid. And it didn't go away by just putting the think in front of him, forcing him to face it, to make him see there is nothing to fear. That totally didn't work at all.
What did work was, holding him on my arm and walking by the Mickey Mouse, not giving it attention as we passed. Or just randomly turning it on, not looking at it anymore. Or all sorts of stuff like that, repeatedly until he decided for himself, that it wasn't anything to be afraid of.
My point is, do not put to much focus on it. It is not something we as adults have to deal with, it is just something we do. Try to see/feel it like that and she will notice your feelings. That is what she did in the first place that made her fear her poo now. The reverse works the same, albeit it takes a bit longer when the fear was already set first.
I would not potty train her for few days until she poos on her normal regular intervals. Then just start over again, not giving it to much attention.
You didn't do it on purpose, and you learned from it (otherwise you wouldn't be knowing what caused it). She will get over it faster then you think. The more she can trust your feelings in it, the faster it is over. I think.